xboard man page

xboard — X graphical user interface for chess


xboard [options]
xboard -ics -icshost hostname [options]
xboard -ncp [options]
cmail [options]


XBoard is a graphical chessboard that can serve as a user interface to chess engines (such as GNU Chess), the Internet Chess Servers, electronic mail correspondence chess, or your own collection of saved games.

This manual documents version 4.9.1 of XBoard.

Major Modes

XBoard always runs in one of four major modes.  You select the major mode from the command line when you start up XBoard.

xboard [options]

As an interface to GNU Chess or another chess engine running on your machine, XBoard lets you play a game against the machine, set up arbitrary positions, force variations, watch a game between two chess engines, interactively analyze your stored games or set up and analyze arbitrary positions. To run engines that use the UCI standard XBoard will draw upon the Polyglot adapter fully transparently, but you will need to have the polyglot package installed for this to work.

xboard -ics -icshost hostname [options]

As Internet Chess Server (ICS) interface, XBoard lets you play against other ICS users, observe games they are playing, or review games that have recently finished.  Most of the ICS "wild" chess variants are supported, including bughouse.

xboard -ncp [options]

XBoard can also be used simply as an electronic chessboard to play through games. It will read and write game files and allow you to play through variations manually. You can use it to browse games off the net or review games you have saved.  These features are also available in the other modes.


If you want to pipe games into XBoard, use the supplied shell script `pxboard'.  For example, from the news reader `xrn', find a message with one or more games in it, click the Save button, and type `|pxboard' as the file name.

cmail [options]

As an interface to electronic mail correspondence chess, XBoard works with the cmail program. See CMail below for instructions.

Basic Operation

To move a piece, you can drag it with the left mouse button, or you can click the left mouse button once on the piece, then once more on the destination square. To under-promote a Pawn you can drag it backwards until it morphs into the piece you want to promote to, after which you drag that forward to the promotion square. Or after selecting the pawn with a first click you can then click the promotion square and move the mouse while keeping the button down until the piece that you want appears in the promotion square. To castle you move the King to its destination or, in Chess960, on top of the Rook you want to castle with. In crazyhouse, bughouse or shogi you can drag and drop pieces to the board from the holdings squares  displayed next to the board.

Old behavior, where right-clicking a square brings up a menu where you can select what piece to drop on it can still be  selected through the `Drop Menu' option. Only in Edit Position mode right and middle clicking a square is still used to put a piece on it, and the piece to drop is selected by sweeping the mouse vertically with the button held down.

The default function of the right mouse button in other modes is  to display the position the chess program thinks it will end up in. While moving the mouse vertically with this button pressed  XBoard will step through the principal variation to show how  this position will be reached. Lines of play displayed in the engine-output window, or PGN variations in the comment window can similarly be played out on the board, by right-clicking on them. Only in Analysis mode, when you walk along a PV,  releasing the mouse button might forward the game upto that point, like you entered all previous PV moves. As the display of the PV in that case starts after the first move a simple right-click will play the move the engine indicates.

In Analysis mode you can also make a move by grabbing the piece with a double-click of the left mouse button (or while keeping the `Ctrl' key pressed). In this case the move you enter will not be played, but will be excluded from the analysis of the current position. (Or included if it was already excluded; it is a toggle.) This only works for engines that support this feature.

When connected to an ICS, it is possible to call up a graphical representation of players seeking a game in stead of the chess board, when the latter is not in use (i.e. when you are not playing or observing). Left-clicking the display area will switch between this 'seek graph' and the chess board. Hovering the mouse pointer over a dot will show the details of the seek ad in the message field above the board. Left-clicking the dot will challenge that player. Right-clicking a dot will 'push it to the back', to reveal any dots that were hidden behind it. Right-clicking off dots will refresh the graph.

Most other XBoard commands are available from the menu bar. The most frequently used commands also have shortcut keys or on-screen buttons. These shortcut keystrokes are mostly non-printable characters. Typing a letter or digit while the board window has focus will bring up a type-in box with the typed letter already in it. You can use that to type a move in situations where it is your turn to enter a move, type a move number to call up the position after that move in the display, or, in Edit Position mode, type a FEN. Some rarely used parameters can only be set through options on the command line used to invoke XBoard.

XBoard uses a settings file, in which it can remember any changes to the settings that are made through menus or command-line options, so they will still apply when you restart XBoard for another session. The settings can be saved into this file automatically when XBoard exits, or on explicit request of the user. Note that the board window can be sized by the user, but that this will not affect the size of the clocks above it, and won't be remembered in the settings file. To persistently change the size of the clocks, use the `size' command-line option when starting XBoard. The default name for the settings file is /etc/xboard/xboard.conf, but in a standard install this file is only used as a master settings file that determines the system-wide default settings, and defers reading and writing of user settings to a user-specific file like ~/.xboardrc in the user's home directory.

When XBoard is iconized, its graphical icon is a white knight if it is White's turn to move, a black knight if it is Black's turn.


This section documents the command-line options to XBoard.  You can set these options in two ways: by typing them on the shell command line you use to start XBoard, or by editing the settings file (usually ~/.xboardrc) to alter the value of the setting that was saved there.  Some of the options cannot be changed while XBoard is running; others set the initial state of items that can be changed with the Options menu.

Most of the options have both a long name and a short name. To turn a boolean option on or off from the command line, either give its long name followed by the value true or false (`-longOptionName true'), or give just the short name to turn the option on (`-opt'), or the short name preceded by `x' to turn the option off (`-xopt'). For options that take strings or numbers as values, you can use the long or short option names interchangeably.

Chess Engine Options

-tc or -timeControl minutes[:seconds]

Each player begins with his clock set to the `timeControl' period. Default: 5 minutes. The additional options `movesPerSession' and `timeIncrement' are mutually exclusive.  

-mps or -movesPerSession moves

When both players have made `movesPerSession' moves, a new `timeControl' period is added to both clocks.  Default: 40 moves.

-inc or -timeIncrement seconds

If this option is specified, `movesPerSession' is ignored. Instead, after each player's move, `timeIncrement' seconds are added to his clock.   Use `-inc 0' if you want to require the entire game to be played in one `timeControl' period, with no increment. Default: -1, which specifies `movesPerSession' mode.

-clock/-xclock or -clockMode true/false

Determines whether or not to display the chess clocks. If clockMode is false, the clocks are not shown, but the side that is to play next is still highlighted. Also, unless `searchTime' is set, the chess engine still keeps track of the clock time and uses it to determine how fast to make its moves.

-shoMoveTime true/false

When this option is set the time that has been thought about the current move will be displayed behind the remaining time in parentheses (in seconds). Default: false.

-st or -searchTime minutes[:seconds]

Tells the chess engine to spend at most the given amount of time searching for each of its moves. Without this option, the chess engine chooses its search time based on the number of moves and amount of time remaining until the next time control. Setting this option also sets clockMode to false.

-depth or -searchDepth number

Tells the chess engine to look ahead at most the given number of moves when searching for a move to make. Without this option, the chess engine chooses its search depth based on the number of moves and amount of time remaining until the next time control.  With the option, the engine will cut off its search early if it reaches the specified depth.

-firstNPS number
-secondNPS number

Tells the chess engine to use an internal time standard based on its node count,  rather then wall-clock time, to make its timing decisions.  The time in virtual seconds should be obtained by dividing the node count  through the given number, like the number was a rate in nodes per second.  Xboard will manage the clocks in accordance with this, relying on the number  of nodes reported by the engine in its thinking output. If the given number equals zero,  it can obviously not be used to convert nodes to seconds, and the time reported  by the engine is used to decrement the XBoard clock in stead. The engine is supposed to  report in CPU time it uses, rather than wall-clock time, in this mode. This option  can provide fairer conditions for engine-engine matches on heavily loaded machines,  or with very fast games (where the wall clock is too inaccurate).  `showThinking' must be on for this option to work. Default: -1 (off). Not many engines might support this yet!

-firstTimeOdds factor
-secondTimeOdds factor

Reduces the time given to the mentioned engine by the given factor.  If pondering is off, the effect is indistinguishable from what would happen  if the engine was running on an n-times slower machine. Default: 1.

-timeOddsMode mode

This option determines how the case is handled where both engines have a time-odds handicap.  If mode=1, the engine that gets the most time will always get the nominal time,  as specified by the time-control options, and its opponent's time is renormalized accordingly.  If mode=0, both play with reduced time. Default: 0.

-hideThinkingFromHuman true/false

Controls the Hide Thinking option. See Options Menu. Default: true. (Replaces the Show-Thinking option of older xboard versions.)

-thinking/-xthinking or -showThinking true/false

Forces the engine to send thinking output to xboard.  Used to be the only way to control if thinking output was displayed  in older xboard versions, but as the thinking output in xboard 4.3 is also used for several other purposes (adjudication, storing in PGN file) the display of it is now controlled by the new option Hide Thinking. See Options Menu. Default: false. (But if xboard needs the thinking output for some purpose, it makes the engine send it despite the setting of this option.)

-ponder/-xponder or -ponderNextMove true/false

Sets the Ponder Next Move menu option. See Options Menu. Default: true.

-smpCores number

Specifies the maximum number of CPUs an SMP engine is allowed to use. Only works for engines that support the XBoard/WinBoard-protocol cores feature.

-mg or -matchGames n

Automatically runs an n-game match between two chess engines, with alternating colors. If the `loadGameFile' or `loadPositionFile' option is set, XBoard starts each game with the given opening moves or the given position; otherwise, the games start with the standard initial chess position. If the `saveGameFile' option is set, a move record for the match is appended to the specified file. If the `savePositionFile' option is set, the final position reached in each game of the match is appended to the specified file. When the match is over, XBoard displays the match score and exits. Default: 0 (do not run a match).

-mm/-xmm or -matchMode true/false

Setting `matchMode' to true is equivalent to setting `matchGames' to 1.

-sameColorGames n

Automatically runs an n-game match between two chess engines, without alternating colors. Otherwise the same applies as for the `-matchGames' option, over which it takes precedence if both are specified. (See there.) Default: 0 (do not run a match).


This option puts XBoard in a special mode for solving EPD test-suites, for the entire duration of the session. In this mode games are aborted after a single move, and that move will be compared with the best-move or avoid-move from the EPD position description from which the 'game' was started. Playing a best move counts as a win, playing an avoid move as a loss, and playing any other move counts as a draw. This option should be used in combination with match mode, and an EPD file of starting positions with an auto-incrementing index. Color assignment will be such that the first engine plays all moves, and the second engine will be never involved. The results for individual positions, as well as the time used for solving them, will be reported in the lower pane of the Engine Output window.

-fcp or -firstChessProgram program
-scp or -secondChessProgram program

Name of first and second chess engine, respectively. A second chess engine is started only in Two Machines (match) mode, or in Analyze mode with two engines. The second engine is by default the same as the first. Default for the first engine: `fairymax'.

-fe or -firstEngine nickname
-se or -secondEngine nickname

This is an alternative to the `fcp' and `scp' options for specifying the first and second engine, for engines that were already registered (using the `Load Engine' dialog) in XBoard's settings file. It will not only retrieve the real name of the engine, but also all options configured with it. (E.g. if it is UCI, whether it should use book.)

-fb/-xfb or -firstPlaysBlack true/false

In games between two chess engines, firstChessProgram normally plays white.  If this option is true, firstChessProgram plays black.  In a multi-game match, this option affects the colors only for the first game; they still alternate in subsequent games.

-fh or -firstHost host
-sh or -secondHost host

Hosts on which the chess engines are to run. The default for each is `localhost'. If you specify another host, XBoard uses `rsh' to run the chess engine there. (You can substitute a different remote shell program for rsh using the `remoteShell' option described below.)

-fd or -firstDirectory dir
-sd or -secondDirectory dir

Working directories in which the chess engines are to be run. The default is "", which means to run the chess engine in the same working directory as XBoard itself.  (See the CHESSDIR environment variable.) This option is effective only when the chess engine is being run on the local host; it does not work if the engine is run remotely using the -fh or -sh option.

-initString string or -firstInitString
-secondInitString string

The string that is sent to initialize each chess engine for a new game. Default:


Setting this option from the command line is tricky, because you must type in real newline characters, including one at the very end. In most shells you can do this by entering a `\' character followed by a newline.  Using the character sequence `\n' in the string should work too, though.

If you change this option, don't remove the `new'  command; it is required by all chess engines to start a new game.

You can remove the `random' command if you like; including it causes GNU Chess 4 to randomize its move selection slightly so that it doesn't play the same moves in every game.  Even without `random', GNU Chess 4 randomizes its choice of moves from its opening book.  Many other chess engines ignore this command entirely and always (or never) randomize.

You can also try adding other commands to the initString; see the documentation of the chess engine you are using for details.

-firstComputerString string
-secondComputerString string

The string that is sent to the chess engine if its opponent is another computer chess engine.  The default is `computer\n'.  Probably the only useful alternative is the empty string (`'), which keeps the engine from knowing that it is playing another computer.

-reuse/-xreuse or -reuseFirst true/false
-reuse2/-xreuse2 or -reuseSecond true/false

If the option is false, XBoard kills off the chess engine after every game and starts it again for the next game.   If the option is true (the default),  XBoard starts the chess engine only once and uses it repeatedly to play multiple games. Some old chess engines may not work properly when reuse is turned on, but otherwise games will start faster if it is left on.

-firstProtocolVersion version-number
-secondProtocolVersion version-number

This option specifies which version of the chess engine communication protocol to use.  By default, version-number is 2.  In version 1, the "protover" command is not sent to the engine; since version 1 is a subset of version 2, nothing else changes.  Other values for version-number are not supported.

-firstScoreAbs true/false
-secondScoreAbs true/false

If this option is set, the score reported by the engine is taken to be  that in favor of white, even when the engine plays black.  Important when XBoard uses the score for adjudications, or in PGN reporting.

-niceEngines priority

This option allows you to lower the priority of the engine processes,  so that the generally insatiable hunger for CPU time of chess engines does not interfere so much  with smooth operation of XBoard (or the rest of your system).  Negative values could increase the engine priority, which is not recommended.

-firstOptions string
-secondOptions string

The given string is a comma-separated list of (option name=option value) pairs,  like the following example: "style=Karpov,blunder rate=0".  If an option announced by the engine at startup through the feature commands of the XBoard/WinBoard protocol  matches one of the option names (i.e. "style" or "blunder rate"),  it would be set to the given value (i.e. "Karpov" or 0)  through a corresponding option command to the engine.  This provided that the type of the value (text or numeric) matches as well.

-firstNeedsNoncompliantFEN string
-secondNeedsNoncompliantFEN string

The castling rights and e.p. fields of the FEN sent to the mentioned engine  with the setboard command will be replaced by the given string. This can for  instance be used to run engines that do not understand Chess960 FENs in  variant fischerandom, to make them at least understand the opening position,  through setting the string to "KQkq -". (Note you also have to give the e.p. field!)  Other possible applications are to provide work-arounds for engines that want to see  castling and e.p. fields in variants that do not have castling or e.p.  (shatranj, courier, xiangqi, shogi) so that XBoard would normally omit them  (string = "- -"), or to add variant-specific fields that are not yet supported by XBoard  (e.g. to indicate the number of checks in 3check).


Forces shuffling of the opening setup in variants that normally have a fixed initial position. Shufflings are symmetric for black and white, and exempt King and Rooks in variants with normal castling. Remains in force until a new variant is selected.


Specifies Fischer castling (as in Chess960) should be enabled in variants that normally would not have it. Remains in force until a new variant is selected.

UCI + WB Engine Settings

-fUCI or -firstIsUCI true/false
-sUCI or -secondIsUCI true/false

Indicates if the mentioned engine executable file is a UCI engine,  and should be run with the aid of the Polyglot adapter rather than directly.  Xboard will then pass the other UCI options and engine name to Polyglot  on its command line, according to the option `adapterCommand'.


Options similar to `fUCI' and `sUCI', except that they use the indicated engine with the protocol adapter specified in the `uxiAdapter' option. This can then be configured for running a UCCI or USI adapter, as the need arises.

-adapterCommand string

The string contains the command that should be issued by XBoard to start an engine that is accompanied by the `fUCI' option. Any identifier following a percent sign in the command (e.g. %fcp) will be considered the name of an XBoard option, and be replaced by the value of that option at the time the engine is started. For starting the second engine, any leading "f" or "first" in the option name will first be replaced by "s" or "second", before finding its value. Default: 'polyglot -noini -ec "%fcp" -ed "%fd"'

-uxiAdapter string

Similar to `adapterCommand', but used for engines accompanied by the `fUCCI' or `fUSI' option, so you can configure XBoard to be ready to handle more than one flavor of non-native protocols. Default: ""

-polyglotDir filename

Gives the name of the directory in which the Polyglot adapter for UCI engines resides. Default: "".

-usePolyglotBook true/false

Specifies if the Polyglot book should be used as GUI book.

-polyglotBook filename

Gives the filename of the opening book. The book is only used when the `usePolyglotBook' option is set to true, and the option `firstHasOwnBookUCI' or `secondHasOwnBookUCI'  applying to the engine is set to false. The engine will be kept in force mode as long as the current position is in book,  and XBoard will select the book moves for it. Default: "".

-fNoOwnBookUCI or -firstXBook or -firstHasOwnBookUCI true/false
-sNoOwnBookUCI or -secondXBook or -secondHasOwnBookUCI true/false

Indicates if the mentioned engine has its own opening book it should play from, rather than using the external book through XBoard.  Default: depends on setting of the option `discourageOwnBooks'.

-discourageOwnBooks true/false

When set, newly loaded engines will be assumed to use the GUI book,  unless they explicitly specify differently. Otherwise they will be assumed to not use the GUI book, unless the specify differently (e.g. with `firstXBook'). Default: false.

-bookDepth n

Limits the use of the GUI book to the first n moves of each side. Default: 12.

-bookVariation n

A value n from 0 to 100 tunes the choice of moves from the GUI books from totally random to best-only. Default: 50


When this volatile option is specified, the probing algorithm of the GUI book is altered to always select the move that is most under-represented based on its performance. When all moves are played in approximately the right proportion, a book miss will be reported, to give the engine opportunity to explore a new move. In addition score of the moves will be kept track of during the session in a book buffer. By playing an match in this mode, a book will be built from scratch. The only output are the saved games, which can be converted to an actual book later, with the `Save Games as Book' command. The latter command can also be used to pre-fill the book buffer before adding new games based on the probing algorithm.

-fn string or -firstPgnName string
-sn string or -secondPgnName string

Indicates the name that should be used for the engine in PGN tags of engine-engine games. Intended to allow you to install versions of the same engine with different settings,  and still distinguish them. Default: "".

-defaultHashSize n

Sets the size of the hash table to n MegaBytes. Together with the EGTB cache size  this number is also used to calculate the memory setting of XBoard/WinBoard engines,  for those that support the memory feature of the XBoard/WinBoard protocol. Default: 64.

-defaultCacheSizeEGTB n

Sets the size of the EGTB cache to n MegaBytes. Together with the hash-table size  this number is also used to calculate the memory setting of XBoard/WinBoard engines,  for those that support the memory feature of the XBoard/WinBoard protocol. Default: 4.

-defaultPathEGTB filename

Gives the name of the directory where the end-game tablebases are installed, for UCI engines. Default: "/usr/local/share/egtb".

-egtFormats string

Specifies which end-game tables are installed on the computer, and where.  The argument is a comma-separated list of format specifications,  each specification consisting of a format name, a colon, and a directory path name,  e.g. "nalimov:/usr/local/share/egtb".  If the name part matches that of a format that the engine requests through a feature command,  xboard will relay the path name for this format to the engine through an egtpath command.  One egtpath command for each matching format will be sent.  Popular formats are "nalimov" and "gaviota" DTM tablebases, syzygy DTZ tablebases and "scorpio" bitbases. Default: "".


This option lets you customize the listbox with chess-engine names  that appears in the `Load Engine' and `Tournament Options' dialog.  It consists of a list of strings, one per line.  When an engine is loaded, the corresponding line is prefixed with "-fcp ", and processed like it appeared on the command line. That means that apart from the engine command, it can contain any number of XBoard options you want to use with this engine. (Commonly used options here are -fd, -firstXBook, -fUCI, -variant.)

The value of this option is gradually built as you load new engines through the `Load Engine' menu dialog, with `Add to list' ticked.  To change it in other ways, (e.g. deleting engines), use the menu item `Edit Engine List' in the `Engine' menu.

Tournament options

-defaultMatchGames n

Sets the number of games that will be used for a match between two engines started from the menu to n. Also used as games per pairing in other tournament formats.  Default: 10.

-matchPause n

Specifies the duration of the pause between two games of a match or tournament between engines as n milliseconds. Especially engines that do not support ping need this option,  to prevent that the move they are thinking on when an opponent unexpectedly resigns will be counted for the next game, (leading to illegal moves there). Default: 10000.

-tf filename or -tourneyFile filename

Specifies the name of the tournament file used in match mode  to conduct a multi-player tournament.  This file is a special settings file,  which stores the description of the tournament (including progress info),  through normal options (e.g. for time control, load and save files),  and through some special-purpose options listed below.

-tt number or -tourneyType number

Specifies the type of tourney: 0 = round-robin,  N>0 = (multi-)gauntlet with N gauntlet engines,  -1 = Swiss through external pairing engine.  Volatile option, but stored in tourney file.

-cy number or -tourneyCycles number

Specifies the number of cycles in a tourney.  Volatile option, but stored in tourney file.

-participants list

The list is a multi-line text string that specifies engines  occurring in the `firstChesProgramNames' list  in the settings file by their (implied or explicitly given) nicknames,  one engine per line.  The mentioned engines will play in the tourney.  Volatile option, but stored in tourney file.

-results string

The string of +=- characters lists the result of all played games in a tourney.  Games currently playing are listed as *,  while a space indicates a game that is not yet played.  Volatile option, but stored in tourney file.

-defaultTourneyName string

Specifies the name of the tournament file XBoard should propose  when the `Match Options' dialog is opened.  Any %y, %M, %d, %h, %m, %s in the string are replaced by the current  year, month, day of the month, hours, minutes, seconds of the current time,  respectively, as two-digit number.  A %Y would be replaced by the year as 4-digit number. Default: empty string.

-pairingEngine filename

Specifies the external program to be used to pair the participants in Swiss tourneys.  XBoard communicates with this engine in the same way as it communicates with Chess engines.  The only commands sent to the pairing engine are “results N string”,  (where N is the number of participants,  and string the results so far in the format of the results option),  and “pairing N”, (where N is the number of the tourney game).  To the latter the pairing engine should answer with “A-B”,  where A and B are participant numbers (in the range 1-N).  (There should be no reply to the results command.) Default: empty string.

-afterGame string
-afterTourney string

When non-empty, the given string will be executed as a system command  after each tournament game, or after the tourney completes, respectively. This can be used, for example, to autmatically run a cross-table generator on the PGN file where games are saved, to update the tourney standings. Default: ""

-syncAfterRound true/false
-syncAfterCycle true/false

Controls whether different instances of XBoard concurrently running the  same tournament will wait for each other. Defaults: sync after cycle, but not after round.

-seedBase number

Used to store the seed of the pseudo-random-number generator in the tourneyFile, so that separate instances of XBoard working on the same tourney can take coherent 'random' decisions, such as picking an opening for a given game number.

ICS options

-ics/-xics or -internetChessServerMode true/false

Connect with an Internet Chess Server to play chess against its other users, observe games they are playing, or review games that have recently finished. Default: false.

-icshost or -internetChessServerHost host

The Internet host name or address of the chess server to connect to when in ICS mode. Default: `chessclub.com'. Another popular chess server to try is `freechess.org'. If your site doesn't have a working Internet name server, try specifying the host address in numeric form.  You may also need to specify the numeric address when using the icshelper option with timestamp or timeseal (see below).

-icsport or -internetChessServerPort port-number

The port number to use when connecting to a chess server in ICS mode. Default: 5000.

-icshelper or -internetChessServerHelper prog-name

An external helper program used to communicate with the chess server. You would set it to "timestamp" for ICC (chessclub.com) or "timeseal" for FICS (freechess.org), after obtaining the correct version of timestamp or timeseal for your computer.  See "help timestamp" on ICC and "help timeseal" on FICS. This option is shorthand for `-useTelnet -telnetProgram program'.

-telnet/-xtelnet or -useTelnet true/false

This option is poorly named; it should be called useHelper. If set to true, it instructs XBoard to run an external program to communicate with the Internet Chess Server.  The program to use is given by the telnetProgram option. If the option is false (the default), XBoard opens a TCP socket and uses its own internal implementation of the telnet protocol to communicate with the ICS. See Firewalls.

-telnetProgram prog-name

This option is poorly named; it should be called helperProgram. It gives the name of the telnet program to be used with the `gateway' and `useTelnet' options.  The default is `telnet'. The telnet program is invoked with the value of `internetChessServerHost' as its first argument and the value of `internetChessServerPort' as its second argument. See Firewalls.

-gateway host-name

If this option is set to a host name, XBoard communicates with the Internet Chess Server by using `rsh' to run the `telnetProgram' on the given host, instead of using its own internal implementation of the telnet protocol. You can substitute a different remote shell program for `rsh' using the `remoteShell' option described below. See Firewalls.

-internetChessServerCommPort or -icscomm dev-name

If this option is set, XBoard communicates with the ICS through the given character I/O device instead of opening a TCP connection. Use this option if your system does not have any kind of Internet connection itself (not even a SLIP or PPP connection), but you do have dial-up access (or a hardwired terminal line) to an Internet service provider from which you can telnet to the ICS.

The support for this option in XBoard is minimal. You need to set all communication parameters and tty modes before you enter XBoard.

Use a script something like this:

    stty raw -echo 9600 > /dev/tty00
    xboard -ics -icscomm /dev/tty00

Here replace `/dev/tty00' with the name of the device that your modem is connected to. You might have to add several more options to these stty commands. See the man pages for `stty' and `tty' if you run into problems. Also, on many systems stty works on its standard input instead of standard output, so you have to use `<' instead of `>'.

If you are using linux, try starting with the script below. Change it as necessary for your installation.

    #!/bin/sh -f
    # configure modem and fire up XBoard
    # configure modem
      stty 2400 ; stty raw ; stty hupcl ; stty -clocal
      stty ignbrk ; stty ignpar ; stty ixon ; stty ixoff
      stty -iexten ; stty -echo
    ) < /dev/modem
    xboard -ics -icscomm /dev/modem

After you start XBoard in this way, type whatever commands are necessary to dial out to your Internet provider and log in. Then telnet to ICS, using a command like `telnet chessclub.com 5000'. Important: See the paragraph below about extra echoes,  in Limitations.

-icslogon or -internetChessServerLogonScript file-name

Whenever XBoard connects to the Internet Chess Server, if it finds a file with the name given in this option, it feeds the file's contents to the ICS as commands. The default file name is `.icsrc'. Usually the first two lines of the file should be your ICS user name and password. The file can be either in $CHESSDIR, in XBoard's working directory if CHESSDIR is not set, or in your home directory.

-msLoginDelay delay

If you experience trouble logging on to an ICS when using the `-icslogon' option, inserting some delay between characters of the logon script may help. This option adds `delay' milliseconds of delay between characters. Good values to try are 100 and 250.

-icsinput/-xicsinput or -internetChessServerInputBox true/false

Sets the ICS Input Box menu option. See Mode Menu. Default: false.

-autocomm/-xautocomm or -autoComment true/false

Sets the Auto Comment menu option. See Options Menu. Default: false.

-autoflag/-xautoflag or -autoCallFlag true/false

Sets the Auto Flag menu option.  See Options Menu. Default: false.

-autobs/-xautobs or -autoObserve true/false

Sets the Auto Observe menu option.  See Options Menu. Default: false.


Enables kibitzing of the engines last thinking output (depth, score, time, speed, PV)  before it moved to the ICS, in zippy mode. The option `showThinking' must be switched on for  this option to work. Also diverts similar kibitz information of an opponent engine that is playing you  through the ICS to the engine-output window, as if the engine was playing locally.

-seekGraph true/false or -sg

Enables displaying of the seek graph by left-clicking the board when you are logged on to an ICS and currently idle. The seek graph show all players currently seeking games on the ICS, plotted according to their rating and the time control of the game they seek, in three different colors (for rated, unrated and wild games). Computer ads are displayed as squares, human ads are dots. Default: false.

-autoRefresh true/false

Enables automatic updating of the seek graph, by having the ICS send a running update of all newly placed and removed seek ads. This consumes a substantial amount of communication bandwidth, and is only supported for FICS and ICC. Default: false.

-backgroundObserve true/false

When true, boards sent to you by the ICS from other games while you are playing (e.g. because you are observing them) will not be automatically displayed. Only a summary of time left and material of both players will appear in the message field above the board. XBoard will remember the last board it has received this way, and will display it instead of the position in your own game when you press the right mouse button. No other information is stored on such games observed in the background; you cannot save such a game later, or step through its moves. This feature is provided solely for the benefit of bughouse players, to enable them to peek at their partner's game without the need to logon twice. Default: false.

-dualBoard true/false

In combination with -backgroundObserve true, this option will display the board of the background game side by side with that of your own game, so you can have it in view permanently. Any board or holdings info coming in will be displayed on the secondary board immediately. This feature is still experimental and largely unfinished. There is no animation or highlighting of moves on the secondary board. Default: false.

-disguisePromotedPieces true/false

When set promoted Pawns in crazyhouse/bughouse are displayed identical to primordial pieces of the same type, rather than distinguishable. Default: true.

-moves/-xmoves or -getMoveList true/false

Sets the Get Move List menu option.  See Options Menu.  Default: true.

-alarm/-xalarm or -icsAlarm true/false

Sets the ICS Alarm menu option.  See Options Menu. Default: true.

-icsAlarmTime ms

Sets the time in milliseconds for the ICS Alarm menu option. See Options Menu. Default: 5000.

lowTimeWarning true/false

Controls a color change of the board as a warning your time is running out. See Options Menu. Default: false.

-pre/-xpre or -premove true/false

Sets the Premove menu option. See Options Menu. Default: true.

-prewhite/-xprewhite or -premoveWhite
-preblack/-xpreblack or -premoveBlack
-premoveWhiteText string
-premoveBlackText string

Set the menu options for specifying the first move for either color.  See Options Menu. Defaults: false and empty strings, so no pre-moves.

-quiet/-xquiet or -quietPlay true/false

Sets the Quiet Play menu option.  See Options Menu.  Default: false.

-colorizeMessages or -colorize/-xcolorize

Setting colorizeMessages to true tells XBoard to colorize the messages received from the ICS.  Colorization works only if your xterm  supports ISO 6429 escape sequences for changing text colors. Default: true.

-colorShout foreground,background,bold
-colorSShout foreground,background,bold
-colorCShout foreground,background,bold
-colorChannel1 foreground,background,bold
-colorChannel foreground,background,bold
-colorKibitz foreground,background,bold
-colorTell foreground,background,bold
-colorChallege foreground,background,bold
-colorRequest foreground,background,bold
-colorSeek foreground,background,bold
-colorNormal foreground,background,bold

These options set the colors used when colorizing ICS messages. All ICS messages are grouped into one of these categories: shout, sshout, channel 1, other channel, kibitz, tell, challenge,  request (including abort, adjourn, draw, pause, and takeback), or normal (all other messages).  

Each foreground or background argument can be one of the following: black, red, green, yellow, blue, magenta, cyan, white, or default. Here “default” means the default foreground or background color of your xterm.  Bold can be 1 or 0.  If background is omitted, “default” is assumed; if bold is omitted, 0 is assumed.

-soundProgram progname

If this option is set to a sound-playing program that is installed and working on your system, XBoard can play sound files when certain events occur, listed below.  The default program name is "play".  If any of the sound options is set to "$", the event rings the terminal bell by sending a ^G character to standard output, instead of playing a sound file.  If an option is set to the empty string "", no sound is played for that event.

-soundDirectory directoryname

This option specifies where XBoard will look for sound files, when these are not given as an absolute path name.

-soundShout filename
-soundSShout filename
-soundCShout filename
-soundChannel filename
-soundChannel1 filename
-soundKibitz filename
-soundTell filename
-soundChallenge filename
-soundRequest filename
-soundSeek filename

These sounds are triggered in the same way as the colorization events described above.  They all default to "", no sound.  They are played only if the colorizeMessages is on. CShout is synonymous with SShout.

-soundMove filename

This sound is played when a player other than yourself makes a move. Default: "$".

-soundRoar filename

This sound is played when a Lion makes a hit-and-run or double capture/ Default: "" (no sound).

-soundIcsAlarm filename

This sound is used by the ICS Alarm menu option.  Default: "$".

-soundIcsWin filename

This sound is played when you win an ICS game.  Default: "" (no sound).

-soundIcsLoss filename

This sound is played when you lose an ICS game.  Default: "" (no sound).

-soundIcsDraw filename

This sound is played when you draw an ICS game.  Default: "" (no sound).

-soundIcsUnfinished filename

This sound is played when an ICS game that you are participating in is aborted, adjourned, or otherwise ends inconclusively.  Default: "" (no sound).

Load and Save options

-lgf or -loadGameFile file
-lgi or -loadGameIndex index

If the `loadGameFile' option is set, XBoard loads the specified game file at startup. The file name `-' specifies the standard input. If there is more than one game in the file, XBoard pops up a menu of the available games, with entries based on their PGN  (Portable Game Notation) tags. If the `loadGameIndex' option is set to `N', the menu is suppressed and the N th game found in the file is loaded immediately. The menu is also suppressed if `matchMode' is enabled or if the game file is a pipe; in these cases the first game in the file is loaded immediately. Use the `pxboard' shell script provided with XBoard if you want to pipe in files containing multiple games and still see the menu. If the loadGameIndex specifies an index -1, this triggers auto-increment of the index in `matchMode', which means that after every game the index is incremented by one, causing each game of the match to be played from the next game in the file. Similarly, specifying an index value of -2 causes the index to be incremented every two games, so that each game in the file is used twice (with reversed colors). The `rewindIndex' option causes the index to be reset to the first game of the file when it has reached a specified value.

-rewindIndex n

Causes a position file or game file to be rewound to its beginning after n positions or games in auto-increment `matchMode'.  See `loadPositionIndex' and `loadGameIndex'. default: 0 (no rewind).

-td or -timeDelay seconds

Time delay between moves during `Load Game' or `Analyze File'.  Fractional seconds are allowed; try `-td 0.4'.  A time delay value of -1 tells XBoard not to step through game files automatically. Default: 1 second.

-sgf or -saveGameFile file

If this option is set, XBoard appends a record of every game played to the specified file. The file name `-' specifies the standard output.

-autosave/-xautosave or -autoSaveGames true/false

Sets the Auto Save menu option.  See Options Menu.  Default: false. Ignored if `saveGameFile' is set.

-onlyOwnGames true/false

Suppresses auto-saving of ICS observed games. Default: false.

-lpf or -loadPositionFile file
-lpi or -loadPositionIndex index

If the `loadPositionFile' option is set, XBoard loads the specified position file at startup. The file name `-' specifies the standard input. If the `loadPositionIndex' option is set to N, the Nth position found in the file is loaded; otherwise the first position is loaded. If the loadPositionIndex specifies an index -1, this triggers auto-increment of the index in `matchMode', which means that after every game the index is incremented by one, causing each game of the match to be played from the next position in the file. Similarly, specifying an index value of -2 causes the index to be incremented every two games, so that each position in the file is used twice (with the engines playing opposite colors). The `rewindIndex' option causes the index to be reset to the first position of the file when it has reached a specified value.

-spf or -savePositionFile file

If this option is set, XBoard appends the final position reached in every game played to the specified file. The file name `-' specifies the standard output.

-positionDir directory

Specifies the directory where file browsing should start when using the `Load Position' menu item.

-pgnExtendedInfo true/false

If this option is set, XBoard saves depth, score and time used for each  move that the engine found as a comment in the PGN file. Default: false.

-pgnTimeLeft true/false

If this option is set, XBoard will save the remaining clock time for the player that has just moved as part of the `pgnExtendedInfo', rather than the time that player thought about his latest move. Default: false.

-pgnEventHeader string

Default: false. Sets the name used in the PGN event tag to string.  Default: "Computer Chess Game".

-pgnNumberTag true/false

Include the (unique) sequence number of a tournament game into the saved PGN file as a 'number' tag. Default: false.

-saveOutOfBookInfo true/false

Include the information on how the engine(s) game out of its opening book  in a special 'annotator' tag with the PGN file. Default: true.

-oldsave/-xoldsave or -oldSaveStyle true/false

Sets the Old Save Style menu option.  See Options Menu.  Default: false.

-gameListTags string

The character string lists the PGN tags that should be printed in the Game List, and their order. The meaning of the codes is e=event, s=site, d=date, o=round, p=players, r=result, w=white Elo, b=black Elo, t=time control, v=variant, a=out-of-book info, c=result comment. Default: "eprd"

-ini or -settingsFile filename
-saveSettingsFile filename

When XBoard encounters an option -settingsFile (or -ini for short), or @filename, it tries to read the mentioned file, and substitutes the contents of it (presumaby more command-line options) in place of the option. In the case of -ini or -settingsFile, the name of a successfully read settings file is also remembered as the file to use for saving settings (automatically on exit, or on user command). An option of the form @filename does not affect saving. The option -saveSettingsFile does specify a name of the file to use for saving, without reading any options from it, and is thus also effective when the file did not exist yet. So the settings will be saved to the file specified in the last -saveSettingsFile or succesfull -settingsFile / -ini command, if any, and in /etc/xboard/xboard.conf otherwise. Usualy the latter is only accessible for the system administrator, though,  and will be used to contain system-wide default settings, amongst which a -saveSettingsFile and -settingsFile options to specify a settings file accessible to the individual user, such as ~/.xboardrc in the user's home directory.

-saveSettingsOnExit true/false

Controls saving of options on the settings file.  See Options Menu. Default: true.

User interface options


Suppresses all GUI functions of XBoard  (to speed up automated ultra-fast engine-engine games, which you don't want to watch).  There will be no board or clock updates, no printing of moves,  and no update of the icon on the task bar in this mode.

-logoSize N

This option controls the drawing of player logos next to the clocks. The integer N specifies the width of the logo in pixels; the logo height will always be half the width. When N = 0, no logos will be diplayed. Default: 0.


Specify the images to be used as player logos when `logoSize' is non-zero, next to the white and black clocks, respectively.

-logoDir filename

When `autoLogo' is set, XBoard will search for a PNG image file with the name of the engine or ICS in the directory specified by `logoDir'. For a human player it will look for a file <username>.png in this directory, but only when ~/.logo.png does not provide one.

-recentEngines number
-recentEngineList list

When the number is larger than zero, it determines how many recently used engines will be appended at the bottom of the `Engines' menu. The engines will be saved in your settings file as the option `recentEngineList', by their nicknames, and the most recently used one will always be sorted to the top. If the list after that is longer than the specified number, the last one is discarded. Changes in the list will only become visible the next session, provided you saved the settings. Default: 6.

-oneClickMove true/false

When set, this option allows you to enter moves by only clicking the to- or from-square, when only a single legal move to or from that square is possible. Double-clicking a piece (or clicking an already selected piece) will instruct that piece to make the only capture it can legally do. Default: false.

-monoMouse true/false

When set button 1 clicks on empty squares in Edit Position mode will be interpreted as button 3 clicks, so they place a piece. Default: false.

-movesound/-xmovesound or -ringBellAfterMoves true/false

Sets the Move Sound menu option.  See Options Menu.  Default: false. For compatibility with old XBoard versions, -bell/-xbell are also  accepted as abbreviations for this option.

-analysisBell N

When N is non-zero, the Move Sound will be played whenever a new PV arrives in analysis mode after more than N seconds of analysis. Default: 0.

-exit/-xexit or -popupExitMessage true/false

Sets the Popup Exit Message menu option.  See Options Menu. Default: true.

-popup/-xpopup or -popupMoveErrors true/false

Sets the Popup Move Errors menu option.  See Options Menu. Default: false.

-queen/-xqueen or -alwaysPromoteToQueen true/false

Sets the Always Queen menu option.  See Options Menu.  Default: false.

-sweepPromotions true/false

Sets the `Almost Always Promote to Queen' menu option.   See Options Menu.  Default: false.

-legal/-xlegal or -testLegality true/false

Sets the Test Legality menu option.  See Options Menu.  Default: true.

-size or -boardSize (sizeName | n1,n2,n3,n4,n5,n6,n7)

Determines how large the board will be, by selecting the pixel size of the pieces and setting a few related parameters. The sizeName can be one of: Titanic, giving 129x129 pixel pieces, Colossal 116x116, Giant 108x108, Huge 95x95, Big 87x87, Large 80x80, Bulky 72x72, Medium 64x64, Moderate 58x58, Average 54x54, Middling 49x49, Mediocre 45x45, Small 40x40, Slim 37x37, Petite 33x33, Dinky 29x29, Teeny 25x25, or Tiny 21x21. Xboard installs with a set of scalable (svg) piece images, which it scales to any of the requested sizes. The square size can further be continuously scaled by sizing the board window, but this only adapts the size of the pieces, and has no effect on the width of the grid lines or the font choice (both of which would depend on he selected boardSize). The default depends on the size of your screen; it is approximately the largest size that will fit without clipping.

You can select other sizes or vary other layout parameters by providing a list of comma-separated values (with no spaces) as the argument. You do not need to provide all the values; for any you omit from the end of the list, defaults are taken from the nearest built-in size. The value `n1' gives the piece size, `n2' the width of the black border between squares, `n3' the desired size for the  clockFont, `n4' the desired size for the coordFont, `n5' the desired size for the messageFont, `n6' the smallLayout flag (0 or 1),  and `n7' the tinyLayout flag (0 or 1).   All dimensions are in pixels. If the border between squares is eliminated (0 width), the various highlight options will not work, as there is nowhere to draw the highlight. If smallLayout is 1 and `titleInWindow' is true,  the window layout is rearranged to make more room for the title. If tinyLayout is 1, the labels on the menu bar are abbreviated to one character each and the buttons in the button bar are made narrower.

-overrideLineGap n

When n >= 0, this forces the width of the black border between squares to n pixels for any board size. Mostly used to suppress the grid entirely by setting n = 0, e.g. in xiangqi or just getting a prettier picture. When n < 0 this the size-dependent width of the grid lines is used. Default: -1.

-coords/-xcoords or -showCoords true/false

Sets the Show Coords menu option.  See Options Menu.  Default: false. The `coordFont' option specifies what font to use.

-autoraise/-xautoraise or -autoRaiseBoard true/false

Sets the Auto Raise Board menu option.  See Options Menu.  Default: true.

-autoflip/-xautoflip or -autoFlipView true/false

Sets the Auto Flip View menu option.  See Options Menu.  Default: true.

-flip/-xflip or -flipView true/false

If Auto Flip View is not set, or if you are observing but not participating in a game, then the positioning of the board at the start of each game depends on the flipView option.  If flipView is false (the default), the board is positioned so that the white pawns move from the bottom to the top; if true, the black pawns move from the bottom to the top. In any case, the Flip menu option (see Options Menu) can be used to flip the board after the game starts.

-title/-xtitle or -titleInWindow true/false

If this option is true, XBoard displays player names (for ICS games) and game file names (for `Load Game') inside its main window. If the option is false (the default), this information is displayed only in the window banner. You probably won't want to set this option unless the information is not showing up in the banner, as happens with a few X window managers.

-buttons/-xbuttons or -showButtonBar True/False

If this option is False, xboard omits the [<<] [<] [P] [>] [>>] button bar from the window, allowing the message line to be wider.  You can still get the functions of these buttons using the menus or their keyboard shortcuts.  Default: true.

-evalZoom factor

The score interval (-1,1) is blown up on the vertical axis of the Evaluation Graph by the given factor. Default: 1

-evalThreshold n

Score below n (centiPawn) are plotted as 0 in the Evaluation Graph. Default: 25

-mono/-xmono or -monoMode true/false

Determines whether XBoard displays its pieces and squares with two colors (true) or four (false). You shouldn't have to specify `monoMode'; XBoard will determine if it is necessary.

-showTargetSquares true/false

Determines whether XBoard can highlight the squares a piece has legal moves to, when you grab that piece with the mouse. Default: false.

-flashCount count
-flashRate rate

These options enable flashing of pieces when they land on their destination square. `flashCount' tells XBoard how many times to flash a piece after it lands on its destination square. `flashRate' controls the rate of flashing (flashes/sec). Abbreviations: `flash' sets flashCount to 3. `xflash' sets flashCount to 0. Defaults:  flashCount=0 (no flashing), flashRate=5.

-highlight/-xhighlight or -highlightLastMove true/false

Sets the Highlight Last Move menu option. See Options Menu. Default: false.

-highlightMoveWithArrow true/false

Sets the Highlight with Arrow menu option. See Options Menu. Default: false.

-blind/-xblind or -blindfold true/false

Sets the Blindfold menu option.  See Options Menu.  Default: false.

-periodic/-xperiodic or -periodicUpdates true/false

Controls updating of current move andnode counts in analysis mode. Default: true.


Causes the PV in thinking output of the mentioned engine to be converted  to SAN before it is further processed. Warning: this might lose engine output not understood by the parser, and uses a lot of CPU power. Default: the PV is displayed exactly as the engine produced it.

-showEvalInMoveHistory true/false

Controls whether the evaluation scores and search depth of engine moves are displayed with the move in the move-history window. Default: true.

-clockFont font

The font used for the clocks. If the option value is a pattern that does not specify the font size, XBoard tries to choose an appropriate font for the board size being used. Default Xaw: -*-helvetica-bold-r-normal--*-*-*-*-*-*-*-*. Default GTK: Sans Bold %d.

-coordFont font

The font used for rank and file coordinate labels if `showCoords' is true. If the option value is a pattern that does not specify the font size, XBoard tries to choose an appropriate font for the board size being used. Default Xaw: -*-helvetica-bold-r-normal--*-*-*-*-*-*-*-*. Default GTK: Sans Bold %d.

-messageFont font

The font used for popup dialogs, menus, etc. If the option value is a pattern that does not specify the font size, XBoard tries to choose an appropriate font for the board size being used. Default Xaw: -*-helvetica-medium-r-normal--*-*-*-*-*-*-*-*. Default GTK: Sans Bold %d

-tagsFont font

The font used in the Edit Tags dialog. If the option value contains %d, XBoard will replace it by an appropriate font for the board size being used. (Only used in GTK build.) Default: Sans Normal %d.

-commentFont font

The font used in the Edit Comment dialog. If the option value contains %d, XBoard will replace it by an appropriate font for the board size being used. (Only used in GTK build.) Default: Sans Normal %d.

-icsFont font

The font used to display ICS output in the ICS  Chat window. As ICS output often contains tables aligned by spaces, a mono-space font is recommended here. If the option value contains %d, XBoard will replace it by an appropriate font for the board size being used. (Only used in GTK build.) Default: Monospace Normal %d.

-moveHistoryFont font

The font used in Move History and Engine Output windows. As these windows display mainly moves, one could use a figurine font here. If the option value contains %d, XBoard will replace it by an appropriate font for the board size being used. (Only used in GTK build.) Default: Sans Normal %d.

-gameListFont font

The font used in the listbox of the Game List window. If the option value contains %d, XBoard will replace it by an appropriate font for the board size being used. (Only used in GTK build.) Default: Sans Bold %d.

-fontSizeTolerance tol

In the font selection algorithm, a nonscalable font will be preferred over a scalable font if the nonscalable font's size differs by `tol' pixels or less from the desired size.  A value of -1 will force a scalable font to always be used if available; a value of 0 will use a nonscalable font only if it is exactly the right size;  a large value (say 1000) will force a nonscalable font to always be used if available.  Default: 4.

-pid or -pieceImageDirectory dir

This options control what piece images xboard uses. XBoard will look in the specified directory for an image in png or svg format for every piece type, with names like BlackQueen.svg, WhiteKnight.svg etc. When neither of these is found (or no valid directory is specified) XBoard will first ty to use an image White/BlackTile.svg in that same directory, and if that is not present either use the svg piece that was installed with it (from the source-tree directory `svg'). Both svg and png images will be scaled by XBoard to the required size, but the png pieces lose much in quality when scaled too much. Default: "".

-inscriptions utf8string

The positions in the utf8string correspond to XBoard's piece types, and for each type a glyph can be defined. This glyph will then be rendered on top of the image for the piece. This is useful in combination with the White/BlackTile.svg images, which could be the image of a blank Shogi tile, for writing the kanji piece name on top of it on the fly. Default: "".

-whitePieceColor color
-blackPieceColor color
-lightSquareColor color
-darkSquareColor color
-highlightSquareColor color
-preoveHighlightColor color
-lowTimeWarningColor color

Colors to use for the pieces, squares, and square highlights. Defaults:

    -whitePieceColor       #FFFFCC
    -blackPieceColor       #202020
    -lightSquareColor      #C8C365
    -darkSquareColor       #77A26D
    -highlightSquareColor  #FFFF00
    -premoveHighlightColor #FF0000
    -lowTimeWarningColor   #FF0000

On a grayscale monitor you might prefer:

    -whitePieceColor       gray100
    -blackPieceColor       gray0
    -lightSquareColor      gray80
    -darkSquareColor       gray60
    -highlightSquareColor  gray100
    -premoveHighlightColor gray70
    -lowTimeWarningColor   gray70

The PieceColor options only work properly if the image files defining the pieces were pure black & white (possibly anti-aliased to produce gray scales and semi-transparancy), like the pieces images that come with the install. Their effect on colored pieces is undefined. The SquareColor option only have an effect when no board textures are used.

-trueColors true/false

When set, this option suppresses the effect  of the PieceColor options mentioned above. This is recommended for images that are already colored.

-useBoardTexture true/false
-liteBackTextureFile filename
-darkBackTextureFile filename

Indicate the png image files to be used for drawing the board squares,  and if they should be used rather than using simple colors. The algorithm for cutting squares out of a given bitmap is such that the picture is perfectly reproduced when a bitmap the size of the complete board is given. If the filename ends in "-NxM.png", with integer N and M, it is assumed to contain a bitmap of a complete board of N files and M ranks, and XBoard will scale it to exactly match the current square size. If N=M=0 it scales the entire bitmap to the size of the board, irrespective of the number of files and ranks of the latter. Without any -NxM suffix textures are only blown up by an integer factor when they are smaller than the square size, or, when the name starts with "xq", too small to cover the complete Xiangqi board. Default: false and ""

-drag/-xdrag or -animateDragging true/false

Sets the Animate Dragging menu option. See Options Menu.  Default: true.

-animate/-xanimate or -animateMoving true/false

Sets the Animate Moving menu option. See Options Menu.  Default: true.

-animateSpeed n

Number of milliseconds delay between each animation frame when Animate Moves is on.

-autoDisplayComment true/false
-autoDisplayTags true/false

If set to true, these options cause the window with the move comments, and the window with PGN tags, respectively, to pop up automatically when such tags or comments are encountered during the replaying a stored or loaded game.  Default: true.

-pasteSelection true/false

If this option is set to true, the Paste Position and Paste Game options paste from the currently selected text.  If false, they paste from the clipboard.  Default: false.

-autoCopyPV true|false

When this option is set, the position displayed on the board when you terminate a PV walk  (initiated by a right-click on board or engine-output window) will be automatically put on the clipboard as FEN. Default: false.

-dropMenu true|false

This option allows you to emulate old behavior,  where the right mouse button brings up the (now deprecated) drop menu  rather than displaying the position at the end of the principal variation.  Default: False.

-pieceMenu true|false

This option allows you to emulate old behavior,  where the right mouse button brings up the (now deprecated) piece menu in Edit Position mode. From this menu you can select the piece to put on the square you clicked to bring up the menu, or select items such as `clear board'. You can also `promote' or `demote' a clicked piece to convert it into an unorthodox piece that is not directly in the menu, or give the move to `black' or `white'.

-variations true|false

When this option is on, you can start new variations in Edit Game or Analyze mode by holding the Shift key down while entering a move. When it is off, the Shift key will be ignored. Default: False.

-appendPV true|false

When this option is on, a button 3 click left of a PV in the Engine Output window will play the first move of that PV in Analyze mode, or as many moves as you walk through it by moving the mouse. Default: False.

-absoluteAnalysisScores true|false

When true, scores on the Engine Output window during analysis will be printed from the white point-of-view, rather than the side-to-move point-of-view. Default: False.

-scoreWhite true|false

When true, scores will always be printed from the white point-of-view,  rather than the side-to-move point-of-view. Default: False.

-memoHeaders true|false

When true, column headers will be displayed in the Engine Output window for the depth, score, time and nodes data. A button 3 click on these headers will hide or show the corresponding data. (Not intended for dynamic use, as already printed data of the current search will not be affected!) Defaul: False.

Adjudication Options

-adjudicateLossThreshold n

If the given value is non-zero, XBoard adjudicates the game as a loss  if both engines agree for a duration of 6 consecutive ply that the score  is below the given score threshold for that engine. Make sure the score  is interpreted properly by XBoard,  using `-firstScoreAbs' and `-secondScoreAbs' if needed.  Default: 0 (no adjudication)

-adjudicateDrawMoves n

If the given value is non-zero, XBoard adjudicates the game as a draw  if after the given number of moves it was not yet decided. Default: 0 (no adjudication)

-checkMates true/false

If this option is set, XBoard detects all checkmates and stalemates,  and ends the game as soon as they occur.  Legality-testing must be switched on for this option to work. Default: true

-testClaims true/false

If this option is set, XBoard verifies all result claims made by engines,  and those who send false claims will forfeit the game because of it.  Legality-testing must be switched on for this option to work. Default: true

-materialDraws true/false

If this option is set, XBoard adjudicates games as draws when there is  no sufficient material left to inflict a checkmate.  This applies to KBKB with like bishops (any number, actually), and to KBK, KNK and KK.  Legality-testing must be switched on for this option to work. Default: true

-trivialDraws true/false

If this option is set, XBoard adjudicates games as draws that cannot be  usually won without opponent cooperation. This applies to KBKB with unlike bishops,  and to KBKN, KNKN, KNNK, KRKR and KQKQ. The draw is called after 6 ply into these end-games,  to allow quick mates that can occur in some exceptional positions to be found by the engines.  KQKQ does not really belong in this category, and might be taken out in the future.  (When bitbase-based adjudications are implemented.)  Legality-testing must be on for this option to work. Default: false

-ruleMoves n

If the given value is non-zero, XBoard adjudicates the game as a draw after the given  number of consecutive reversible moves. Engine draw claims are always accepted after 50 moves,  irrespective of the given value of n.

-repeatsToDraw n

If the given value is non-zero, xboard adjudicates the game as a draw if a position  is repeated the given number of times. Engines draw claims are always accepted after 3 repeats,  (on the 3rd occurrence, actually), irrespective of the value of n.  Beware that positions that have different castling or en-passant rights do not count  as repeats, XBoard is fully e.p. and castling aware!

Install options

--show-config parameter

When called with this option, XBoard will close immediately after printing the value of the indicated configuration parameter, or, when no parameter was given, after printing a list of all such parameters. Currently the only valid values for parameter are Datadir and Sysconfdir. This option can be used by install scripts for board themes to figure out where the currently active XBoard stores its data.

-date timestamp
-saveDate timestamp

These options specify an epoch as an integer number. The `saveDate' option is written by XBoard in the settings file every time the settings are saved, with the current time, so that later runs of XBoard can know this. The `date' option can be included in settings files to indicate when lines following it were added to those files. Some options will be ignored if the epoch specified by the latest `date' option predates the -saveDate setting (implying they must have been seen before).

-autoInstall list

When the list is set to a non-empty string, XBoard will scan the operating system's plugin directory for engines supporting UCI and XBoard protocol at startup. When it finds an engine that was installed after it last saved its settings, a line to launch that engine (as per specs in the plugin file) is appended to the -firstChessProgramNames list of installed engines. In the future it will be possible to use the autoInstall list to limit this automatic adding of engines based on the chess variant they play.

-addMasterOption string

Adds the mentioned string as an additional line of XBoard's master settings file, after adding a line with a `date' option to timestamp it. Intended to add options of the 'install' type (see below) to the master file, which will then be processed by any XBoard that has not seen them since it last saved its settings.


The presence of this option cause XBoard to close immediately after processing all its options (from settings file and command line). Typically used from install scripts together with options that change XBoard's settings files, so that XBoard can be run in batch mode rather than interactively.

-installEngine string

Adds the given string as an additional line to the value of the `firstChessProgramNames' option when the -saveDate setting preceeds the -date setting. Intended for adding to the master settings file with the aid of -addMasterOption in the install script of engines, as a method for broadcasting the presence of a new engine to all users, which would then see it automatically registered with XBoard. Made obsolete by the advent of the plugin standard (see the `autoInstall' option), which broadcasts such presence in a non-XBoard-specific way by dropping *.eng files in a certain system directory.

-installTheme string

Adds the given string as an additional line to the value of the -themeNames option when the -saveDate setting preceeds the -date setting. Intended for adding to the master settings file with the aid of -addMasterOption in the install script of board graphics themes, as a method for broadcasting the availability of a new theme to all users, who would then see the theme appear automatically in the listbox in the View Board menu dialog next time they run XBoard.

Other options

-ncp/-xncp or -noChessProgram true/false

If this option is true, XBoard acts as a passive chessboard; it does not start a chess engine at all. Turning on this option also turns off clockMode. Default: false.

-viewerOptions string

Presence of the volatile option `viewer' on the command line will cause the value of the persistent option `viewerOptions' as stored in the settings file to be appended to the command line. The `view' option will be used by desktop associations with game or position file types, so that `viewerOptions' can be used to configure the exact mode XBoard will start in when it should act on such a file (e.g. in -ncp mode, or analyzing with your favorite engine). The options are also automatically appended when Board is invoked with a single argument not being an option name, which is then assumed to be the name of a `loadGameFile' or (when the name ends in .fen) a `loadPositionFile'. Default: "-ncp -engineOutputUp false -saveSettingsOnExit false".

-tourneyOptions string

When XBoard is invoked with a single argument that is a file with .trn extension, it will assume this argument to be the value of a `tourneyFile' option, and append the value of the persistent option `tourneyOptions' as stored in the settings file to the command line. Thus the value of `tourneyOptions' can be used to configure XBoard to automatically start running a tournament when it should act on such a file. Default: "-ncp -mm -saveSettingsOnExit false".

-mode or -initialMode modename

If this option is given, XBoard selects the given modename from the Mode menu after starting and (if applicable) processing the loadGameFile or loadPositionFile option. Default: "" (no selection).  Other supported values are  MachineWhite, MachineBlack, TwoMachines, Analysis,  AnalyzeFile, EditGame, EditPosition, and Training.

-variant varname

Activates  (sometimes partial) support for playing chess variants against a local engine or editing variant games.  This flag is not needed in ICS mode.  Recognized variant names are:

    normal        Normal chess
    wildcastle    Shuffle chess, king can castle from d file
    nocastle      Shuffle chess, no castling allowed
    fischerandom  Fischer Random shuffle chess
    bughouse      Bughouse, ICC/FICS rules
    crazyhouse    Crazyhouse, ICC/FICS rules
    losers        Lose all pieces or get mated (ICC wild 17)
    suicide       Lose all pieces including king (FICS)
    giveaway      Try to have no legal moves (ICC wild 26)
    twokings      Weird ICC wild 9
    kriegspiel    Opponent's pieces are invisible
    atomic        Capturing piece explodes (ICC wild 27)
    3check        Win by giving check 3 times (ICC wild 25)
    shatranj      An ancient precursor of chess (ICC wild 28)
    xiangqi       Chinese Chess (on a 9x10 board)
    shogi         Japanese Chess (on a 9x9 board & piece drops) 
    capablanca    Capablanca Chess (10x8 board, with Archbishop 
                  and Chancellor pieces)
    gothic        similar, with a better initial position
    caparandom    An FRC-like version of Capablanca Chess (10x8) 
    janus         A game with two Archbishops (10x8 board)
    courier       Medieval intermediate between shatranj and 
                  modern Chess (on 12x8 board) 
    falcon        Patented 10x8 variant with two Falcon pieces
    berolina      Pawns capture straight ahead, and move diagonally 
    cylinder      Pieces wrap around the board edge
    knightmate    King moves as Knight, and vice versa 
    super         Superchess (shuffle variant with 4 exo-pieces)
    makruk        Thai Chess (shatranj-like, P promotes on 6th rank)
    asean         ASEAN Chess (a modernized version of Makruk)
    spartan       Spartan Chess (black has unorthodox pieces)
    great         Great Shatranj, a 10x8 variant without sliders
    grand         Grand Chess, on 10x10 with Capablanca pieces
    lion          Mighty-Lion Chess, with a multi-capturing Lion
    elven         Eleven Chess, with Lion and crowned sliders on 10x10
    chu           Chu Shogi, historic 12x12 variant with 2x46 pieces
    fairy         A catchall variant in which all piece types 
                  known to XBoard can participate (8x8)
    unknown       Catchall for other unknown variants

In the shuffle variants, XBoard does shuffle the pieces, although you can still do it by hand using Edit Position.  Some variants are supported only in ICS mode, including bughouse, and kriegspiel. Berolina and cylinder chess are only partially supported, and can only be played with legality testing off.

Apart from these standard variants, engines can define variants of arbitrary names, briefing XBoard transparently on the rules for piece movement, board size and initial setup, so that they work nearly as well as fully-supported standard variants. (But obviously only while using that engine.) The user might have to alter the adjudication settings for some variants, however. E.g. it makes no sense to adjudicate a draw after 50 reversible moves in variants that have a 64-move rule, or no similar rule at all.

Default: "normal". Except when the first engine gave an explicit list of variants it supports, and 'normal' is not amongst those. In that case the first variant the engine mentioned it did play will be chosen.

-boardHeight N

Allows you to set a non-standard number of board ranks in any variant.  If the height is given as -1, the default height for the variant is used. Default: -1

-boardWidth N

Allows you to set a non-standard number of board files in any variant.  If the width is given as -1, the default width for the variant is used.  With a non-standard width, the initial position will always be an empty board,  as the usual opening array will not fit. Default: -1

-holdingsSize N

Allows you to set a non-standard size for the holdings in any variant.  If the size is given as -1, the default holdings size for the variant is used.  The first N piece types will go into the holdings on capture, and you will be  able to drop them on the board in stead of making a normal move. If size equals 0,  there will be no holdings. Default: -1

-defaultFrcPosition N

Specifies the number of the opening position in shuffle games like Chess960.  A value of -1 means the position is randomly generated by XBoard at the beginning of every game. Default: -1

-pieceToCharTable string

The characters that are used to represent the piece types XBoard knows in FEN  diagrams and SAN moves. You should not have to use this option often: each variant has its own default  setting for the piece representation in FEN, which should be sufficient in normal use. The string argument has to specify an even number of pieces  (or it will be ignored), as white and black pieces have to be given separately  (in that order). The last letter for each color will be the King.  The letters before that will be PNBRQ and then a whole host of fairy pieces  in an order that has not fully crystallized yet (currently FEACWMOHIJGDVLSU,  F=Ferz, Elephant, A=Archbishop, C=Chancellor, W=Wazir, M=Commoner, O=Cannon,  H=Nightrider). You should list at least all pieces that occur in the variant  you are playing. If you have fewer characters in the string than XBoard has pieces, the pieces not mentioned will get assigned a period, and will not be usable in the variant. You can also explicitly assign pieces a period, in which case they  will not be counted in deciding which captured pieces can go into the holdings. A tilde '~' as a piece name does mean this piece is used to represent a promoted  Pawn in crazyhouse-like games, i.e. on capture it turns back to a Pawn.  A '+' similarly indicates the piece is a shogi-style promoted piece, that should  revert to its non-promoted version on capture (rather than to a Pawn). By default the second 11 pieces known to XBoard are the promoted forms of the first 11. A piece specified by the character combination ^ plus letter will be assumed to be the promoted form of the piece indicated by that letter, and get a '+' assigned. To get around the limitation of the alphabet, piece IDs can also be 'dressed letters', i.e. a single letter (upper case for white, lower case for black) followed by a single quote or an exclamation point. Default: "" (meaning the default for the variant is used).

-pieceNickNames string

The characters in the string are interpreted the same way as in the `pieceToCharTable' option. But on input, piece-ID letters are first looked up in the nicknames, and only if not defined there, in the normal pieceToCharTable. This allows you to have two letters designate the same piece, (e.g. N as an alternative to H for Horse in Xiangqi), to make reading of non-compliant notations easier. Default: ""

-colorNickNames string

The side-to-move field in a FEN will be first matched against the letters in the string (first character for white, second for black), before it is matched to the regular 'w' and 'b'. This makes it easier to read non-compliant FENs, which, say, use 'r' for white. Default: ""

-debug/-xdebug or -debugMode true/false

Turns on debugging printout.

-debugFile filename or -nameOfDebugFile filename

Sets the name of the file to which XBoard saves debug information  (including all communication to and from the engines). A `%d' in the given file name (e.g. game%d.debug) will be replaced by the unique sequence number of a tournament game, so that the debug output of each game will be written on a separate file.

-engineDebugOutput number

Specifies how XBoard should handle unsolicited output from the engine,  with respect to saving it in the debug file.  The output is further (hopefully) ignored.  If number=0, XBoard refrains from writing such spurious output to the debug file.  If number=1, all engine output is written faithfully to the debug file.  If number=2, any protocol-violating line is prefixed with a '#' character,  as the engine itself should have done if it wanted to submit info for inclusion in the debug file. This option is provided for the benefit of applications that use the debug file  as a source of information, such as the broadcaster of live games TLCV / TLCS.  Such applications can be protected from spurious engine output that might otherwise confuse them.

-rsh or -remoteShell shell-name

Name of the command used to run programs remotely. The default is `rsh' or `remsh', determined when XBoard is configured and compiled.

-ruser or -remoteUser user-name

User name on the remote system when running programs with the `remoteShell'. The default is your local user name.

-userName username

Name under which the Human player will be listed in the PGN file.  Default is the login name on your local computer.

-delayBeforeQuit number
-delayAfterQuit number

These options order pauses before and after sending the "quit" command to an engine that must be terminated. The pause between quit and the previous command is specified in milliseconds. The pause after quit is used to schedule a kill signal to be sent to the engine process after the number of specified seconds plus one. This signal is a different one as the terminiation signal described in the protocol specs which engines can suppress or ignore, and which is sent directly after the "quit" command. Setting `delayAfterQuit' to -1 will suppress sending of the kill signal. Default: 0

-searchMode n

The integer n encodes the mode for the `find position' function. Default: 1 (= Exact position match)

-eloThresholdBoth elo
-eloThresholdAny elo

Defines a lower limit for the Elo rating, which has to be surpassed before a game will be considered when searching for a board position. Default: 0

-dateThreshold year

Only games not played before the given year will be considered when searching for a board position

Chess Servers

An "Internet Chess Server", or "ICS", is a place on the Internet where people can get together to play chess, watch other people's games, or just chat.  You can use either `telnet' or a client program like XBoard to connect to the server.  There are thousands of registered users on the different ICS hosts, and it is not unusual to meet 200 on both chessclub.com and freechess.org.

Most people can just type `xboard -ics' to start XBoard as an ICS client.  Invoking XBoard in this way connects you to the Internet Chess Club (ICC), a commercial ICS.  You can log in there as a guest even if you do not have a paid account.  To connect to the largest Free ICS (FICS), use the command `xboard -ics -icshost freechess.org' instead, or substitute a different host name to connect to your favorite ICS. For a full description of command-line options that control  the connection to ICS and change the default values of ICS options, see ICS options.  

While you are running XBoard as an ICS client, you use the terminal window that you started XBoard from as a place to type in commands and read information that is not available on the chessboard.

The first time you need to use the terminal is to enter your login name and password, if you are a registered player. (You don't need to do this manually; the `icsLogon' option can do it for you. See ICS options.)  If you are not registered,  enter `g' as your name, and the server will pick a unique guest name for you.

Some useful ICS commands include

help <topic>

to get help on the given <topic>. To get a list of possible topics type "help" without topic.  Try the help command before you ask other people on the server for help.

For example `help register' tells you how to become a registered ICS player.

who <flags>

to see a list of people who are logged on.  Administrators (people you should talk to if you have a problem) are marked with the character `*', an asterisk. The <flags> allow you to display only selected players: For example, `who of' shows a list of players who are interested in playing but do not have an opponent.


to see what games are being played

match <player> [<mins>] [<inc>]

to challenge another player to a game. Both opponents get <mins> minutes for the game, and <inc> seconds will be added after each move. If another player challenges you, the server asks if you want to accept the challenge; use the `accept' or `decline' commands to answer.


to accept or decline another player's offer.  The offer may be to start a new game, or to agree to a  `draw', `adjourn' or `abort' the current game. See Action Menu.

If you have more than one pending offer (for example, if more than one player is challenging you, or if your opponent offers both a draw and to adjourn the game), you have to supply additional information, by typing something like `accept <player>', `accept draw', or `draw'.


asks your opponent to terminate a game by mutual agreement. Adjourned games can be continued later.  Your opponent can either `decline' your offer or accept it (by typing the same command or typing `accept').  In some cases these commands work immediately, without asking your opponent to agree.  For example, you can abort the game unilaterally if your opponent is out of time, and you can claim a draw by repetition or the 50-move rule if available simply by typing  `draw'.

finger <player>

to get information about the given <player>. (Default: yourself.)


to get a list of personal settings

set <var> <value>

to modify these settings

observe <player>

to observe an ongoing game of the given <player>.


to review a recently completed game

Some special XBoard features are activated when you are in examine mode on ICS.  See the descriptions of the menu commands `Forward', `Backward', `Pause', `ICS Client',  and `Stop Examining' on the Edit Menu, Mode Menu, and Action Menu.


By default, XBoard communicates with an Internet Chess Server by opening a TCP socket directly from the machine it is running on to the ICS. If there is a firewall between your machine and the ICS, this won't work. Here are some recipes for getting around common kinds of firewalls using special options to XBoard. Important: See the paragraph in the below about extra echoes, in Limitations.

Suppose that you can't telnet directly to ICS, but you can telnet to a firewall host, log in, and then telnet from there to ICS. Let's say the firewall is called `firewall.example.com'. Set command-line options as follows:

    xboard -ics -icshost firewall.example.com -icsport 23

Then when you run XBoard in ICS mode, you will be prompted to log in to the firewall host. This works because port 23 is the standard telnet login service. Do so, then telnet to ICS, using a command like `telnet chessclub.com 5000', or whatever command the firewall provides for telnetting to port 5000.

If your firewall lets you telnet (or rlogin) to remote hosts but doesn't let you telnet to port 5000, you may be able to connect to the chess server on port 23 instead, which is the port the telnet program uses by default.  Some chess servers support this (including chessclub.com and freechess.org), while some do not.

If your chess server does not allow connections on port 23 and your firewall does not allow you to connect to other ports, you may be able to connect by hopping through another host outside the firewall that you have an account on.  For instance, suppose you have a shell account at `foo.edu'. Follow the recipe above, but instead of typing `telnet chessclub.com 5000' to the firewall, type `telnet foo.edu' (or `rlogin foo.edu'), log in there, and then type `telnet chessclub.com 5000'.

Suppose that you can't telnet directly to ICS, but you can use rsh to run programs on a firewall host, and that host can telnet to ICS. Let's say the firewall is called `rsh.example.com'. Set command-line options as follows:

    xboard -ics -gateway rsh.example.com -icshost chessclub.com

Then when you run XBoard in ICS mode, it will connect to the ICS by using `rsh' to run the command `telnet chessclub.com 5000' on host `rsh.example.com'.

Suppose that you can telnet anywhere you want, but you have to run a special program called `ptelnet' to do so.

First, we'll consider the easy case, in which `ptelnet chessclub.com 5000' gets you to the chess server. In this case set command line options as follows:

    xboard -ics -telnet -telnetProgram ptelnet

Then when you run XBoard in ICS mode, it will issue the command `ptelnet chessclub.com 5000' to connect to the ICS.

Next, suppose that `ptelnet chessclub.com 5000' doesn't work; that is, your `ptelnet' program doesn't let you connect to alternative ports. As noted above, your chess server may allow you to connect on port 23 instead.  In that case, just add the option `-icsport ""' to the above command. But if your chess server doesn't let you connect on port 23, you will have to find some other host outside the firewall and hop through it. For instance, suppose you have a shell account at `foo.edu'. Set command line options as follows:

    xboard -ics -telnet -telnetProgram ptelnet -icshost foo.edu -icsport ""

Then when you run XBoard in ICS mode, it will issue the command `ptelnet foo.edu' to connect to your account at `foo.edu'. Log in there, then type `telnet chessclub.com 5000'.

ICC timestamp and FICS timeseal do not work through some firewalls.  You can use them only if your firewall gives a clean TCP connection with a full 8-bit wide path.  If your firewall allows you to get out only by running a special telnet program, you can't use timestamp or timeseal across it.  But if you have access to a computer just outside your firewall, and you have much lower netlag when talking to that computer than to the ICS, it might be worthwhile running timestamp there.  Follow the instructions above for hopping through a host outside the firewall (foo.edu in the example), but run timestamp or timeseal on that host instead of telnet.

Suppose that you have a SOCKS firewall that will give you a clean 8-bit wide TCP connection to the chess server, but only after you authenticate yourself via the SOCKS protocol.  In that case, you could make a socksified version of XBoard and run that.  If you are using timestamp or timeseal, you will to socksify it, not XBoard; this may be difficult seeing that ICC and FICS do not provide source code for these programs.  Socksification is beyond the scope of this document, but see the SOCKS Web site at http://www.socks.permeo.com/. If you are missing SOCKS, try http://www.funbureau.com/.

Environment Variables

Game and position files are found in a directory named by the `CHESSDIR' environment variable. If this variable is not set, the current working directory is used. If `CHESSDIR' is set, XBoard actually changes its working directory to `$CHESSDIR', so any files written by the chess engine will be placed there too.

Limitations and Known Bugs

There is no way for two people running copies of XBoard to play each other without going through an Internet Chess Server.

Under some circumstances, your ICS password may be echoed when you log on.

If you are connecting to the ICS by running telnet on an Internet provider or firewall host, you may find that each line you type is echoed back an extra time after you hit <Enter>. If your Internet provider is a Unix system, you can probably turn its echo off by typing `stty -echo' after you log in, and/or typing <^E><Enter> (Ctrl+E followed by the Enter key) to the telnet program after you have logged into ICS.  It is a good idea to do this if you can, because the extra echo can occasionally confuse XBoard's parsing routines.

The game parser recognizes only algebraic notation.

Many of the following points used to be limitations in XBoard 4.2.7 and earlier,  but are now fixed: The internal move legality tester in XBoard 4.3.xx does look at the game history,  and is fully aware of castling or en-passant-capture rights. It permits castling with  the king on the d file because this is possible in some "wild 1" games on ICS.  The piece-drop menu does not check piece drops in bughouse to see if you actually hold  the piece you are trying to drop. But this way of dropping pieces should be considered  an obsolete feature, now that pieces can be dropped by dragging them from the holdings  to the board. Anyway, if you would attempt an illegal move when using a chess engine or the ICS,  XBoard will accept the error message that comes back, undo the move, and let you try another. FEN positions saved by XBoard do include correct information about whether castling or  en passant are legal, and also handle the 50-move counter. The mate detector does not understand that non-contact mate is not really mate in bughouse.  The only problem this causes while playing is minor: a "#" (mate indicator) character will  show up after a non-contact mating move in the move list. XBoard will not assume the game  is over at that point, not even when the option Detect Mates is on. Edit Game mode always uses the rules of the selected variant,  which can be a variant that uses piece drops.   You can load and edit games that contain piece drops.  The (obsolete) piece menus are not active,  but you can perform piece drops by dragging pieces from the holdings. Fischer Random castling is fully understood.  You can enter castlings by dragging the King on top of your Rook.  You can probably also play Fischer Random successfully on ICS by typing  castling moves into the ICS Interaction window.

The menus may not work if your keyboard is in Caps Lock or Num Lock mode. This seems to be a problem with the Athena menu widget, not an XBoard bug.

Also see the ToDo file included with the distribution for many other possible bugs, limitations, and ideas for improvement that have been suggested.

Reporting Problems

You can report bugs and problems with XBoard using the bug tracker at `https://savannah.gnu.org/projects/xboard/' or by sending mail to `<bug-xboard@gnu.org>'.  It can also be useful to report or discuss bugs in the WinBoard Forum at `http://www.open-aurec.com/wbforum/',  WinBoard development section.

Please use the `script' program to start a typescript, run  XBoard with the `-debug' option, and include the typescript output in your message. Also tell us what kind of machine and what operating system version you are using.  The command `uname -a' will often tell you this.

If you improve XBoard, please send a message about your changes, and we will get in touch with you about merging them in to the main line of development.

Authors and Contributors

Chris Sears and Dan Sears wrote the original XBoard.  They were responsible for versions 1.0 through 1.2.  The color scheme was taken from Wayne Christopher's `XChess' program.

Tim Mann was primarily responsible for XBoard versions 1.3 through 4.2.7, and for WinBoard (a port of XBoard to Microsoft Win32) from its inception through version 4.2.7.

John Chanak contributed the initial implementation of ICS mode.  Evan Welsh wrote `CMail', and Patrick Surry helped in designing, testing, and documenting it.  Elmar Bartel contributed the new piece bitmaps introduced in version 3.2.  Jochen Wiedmann converted the documentation to texinfo.  Frank McIngvale added click/click moving, the Analysis modes, piece flashing, ZIICS import, and ICS text colorization to XBoard.  Hugh Fisher added animated piece movement to XBoard, and Henrik Gram added it to WinBoard.  Mark Williams contributed the initial (WinBoard-only) implementation of many new features added to both XBoard and WinBoard in version 4.1.0, including copy/paste, premove, icsAlarm, autoFlipView, training mode, auto raise, and blindfold.  Ben Nye contributed X copy/paste code for XBoard.

In a fork from version 4.2.7, Alessandro Scotti added many elements to the user interface of WinBoard, including the board textures and font-based rendering, the evaluation-graph, move-history and engine-output window.  He was also responsible for adding the UCI support.

H. G. Muller continued this fork of the project, producing version 4.3.  He made WinBoard castling- and e.p.-aware, added variant support with adjustable board sizes, the crazyhouse holdings, and the fairy pieces.  In addition he added most of the adjudication options, made WinBoard more robust in dealing with buggy and crashing engines, and extended time control with a time-odds and node-count-based modes. Most of the options that initially were WinBoard only have now been back-ported to XBoard.

Michel van den Bergh provided the code for reading Polyglot opening books.

Meanwhile, some work continued on the GNU XBoard project maintained at savannah.gnu.org, but version 4.2.8 was never released.  Daniel Mehrmann was responsible for much of this work.

Most recently, Arun Persaud worked with H. G. Muller to merge all the features of the never-released XBoard/WinBoard 4.2.8 of the GNU XBoard project and the never-released 4.3.16 from H. G.'s fork into a unified XBoard/WinBoard 4.4, which is now available both from the savannah.gnu.org web site and the WinBoard forum.


The `cmail' program can help you play chess by email with opponents of your choice using XBoard as an interface.

You will usually run `cmail' without giving any options.

CMail options


Displays `cmail' usage information.


Shows the conditions of the GNU General Public License. See Copying.


Shows the warranty notice of the GNU General Public License. See Copying.


Provides or inhibits verbose output from `cmail' and XBoard, useful for debugging. The `-xv' form also inhibits the cmail introduction message.


Invokes or inhibits the sending of a mail message containing the move.


Invokes or inhibits the running of XBoard on the game file.


Invokes or inhibits the reuse of an existing XBoard to display the current game.


Resends the last mail message for that game. This inhibits running XBoard.

-game <name>

The name of the game to be processed.

-wgames <number>
-bgames <number>
-games <number>

Number of games to start as White, as Black or in total. Default is 1 as white and none as black. If only one color is specified then none of the other color is assumed. If no color is specified then equal numbers of White and Black games are started, with the extra game being as White if an odd number of total games is specified.

-me <short name>
-opp <short name>

A one-word alias for yourself or your opponent.

-wname <full name>
-bname <full name>
-myname <full name>
-oppname <full name>

The full name of White, Black, yourself or your opponent.

-wna <net address>
-bna <net address>
-na <net address>
-oppna <net address>

The email address of White, Black, yourself or your opponent.

-dir <directory>

The directory in which `cmail' keeps its files. This defaults to the environment variable `$CMAIL_DIR' or failing that, `$CHESSDIR', `$HOME/Chess' or `~/Chess'. It will be created if it does not exist.

-arcdir <directory>

The directory in which `cmail' archives completed games. Defaults to the environment variable `$CMAIL_ARCDIR' or, in its absence, the same directory as cmail keeps its working files (above).

-mailprog <mail program>

The program used by cmail to send email messages. This defaults to the environment variable `$CMAIL_MAILPROG' or failing that `/usr/ucb/Mail', `/usr/ucb/mail' or `Mail'. You will need to set this variable if none of the above paths fit your system.

-logFile <file>

A file in which to dump verbose debugging messages that are invoked with the `-v' option.

-event <event>

The PGN Event tag (default `Email correspondence game').

-site <site>

The PGN Site tag (default `NET').

-round <round>

The PGN Round tag (default `-', not applicable).

-mode <mode>

The PGN Mode tag (default `EM', Electronic Mail).

Other options

Any option flags not listed above are passed through to XBoard. Invoking XBoard through CMail changes the default values of two XBoard options: The default value for `-noChessProgram' is changed to true; that is, by default no chess engine is started.  The default value for `-timeDelay' is changed to 0; that is, by default XBoard immediately goes to the end of the game as played so far, rather than stepping through the moves one by one.  You can still set these options to whatever values you prefer by supplying them on CMail's command line.  See Options.

Starting a CMail Game

Type `cmail' from a shell to start a game as white. After an opening message, you will be prompted for a game name, which is optional -- if you simply press <Enter>, the game name will take the form `you-VS-opponent'. You will next be prompted for the short name of your opponent. If you haven't played this person before, you will also be prompted for his/her email address. `cmail' will then invoke XBoard in the background. Make your first move and select `Mail Move' from the `File' menu. See File Menu. If all is well, `cmail' will mail a copy of the move to your opponent. If you select `Exit' without having selected `Mail Move' then no move will be made.

Answering a Move

When you receive a message from an opponent containing a move in one of your games, simply pipe the message through `cmail'. In some mailers this is as simple as typing `| cmail' when viewing the message, while in others you may have to save the message to a file and do `cmail < file' at the command line. In either case `cmail' will display the game using XBoard. If you didn't exit XBoard when you made your first move then `cmail' will do its best to use the existing XBoard instead of starting a new one. As before, simply make a move and select `Mail Move' from the `File' menu. See File Menu. `cmail' will try to use the XBoard that was most recently used to display the current game. This means that many games can be in progress simultaneously, each with its own active XBoard.

If you want to look at the history or explore a variation, go ahead, but you must return to the current position before XBoard will allow you to mail a move. If you edit the game's history you must select `Reload Same Game' from the `File' menu to get back to the original position, then make the move you want and select `Mail Move'. As before, if you decide you aren't ready to make a move just yet you can either select `Exit' without sending a move or just leave XBoard running until you are ready.

Multi-Game Messages

It is possible to have a `cmail' message carry more than one game. This feature was implemented to handle IECG (International Email Chess Group) matches, where a match consists of one game as white and one as black, with moves transmitted simultaneously. In case there are more general uses, `cmail' itself places no limit on the number of black/white games contained in a message; however, XBoard does.

Completing a Game

Because XBoard can detect checkmate and stalemate, `cmail' handles game termination sensibly. As well as resignation, the `Action' menu allows draws to be offered and accepted for `cmail' games.

For multi-game messages, only unfinished and just-finished games will be included in email messages. When all the games are finished, they are archived in the user's archive directory, and similarly in the opponent's when he or she pipes the final message through `cmail'. The archive file name includes the date the game was started.

Known CMail Problems

It's possible that a strange conjunction of conditions may occasionally mean that `cmail' has trouble reactivating an existing XBoard. If this should happen, simply trying it again should work. If not, remove the file that stores the XBoard's PID (`game.pid') or use the `-xreuse' option to force `cmail' to start a new XBoard.

Versions of `cmail' after 2.16 no longer understand the old file format that XBoard used to use and so cannot be used to correspond with anyone using an older version.

Versions of `cmail' older than 2.11 do not handle multi-game messages, so multi-game correspondence is not possible with opponents using an older version.

Other Programs You Can Use with Xboard

Here are some other programs you can use with XBoard

GNU Chess

The GNU Chess engine is available from:


You can use XBoard to play a game against GNU Chess, or to interface GNU Chess to an ICS.


Fairy-Max is a derivative from the once World's smallest Chess program micro-Max, which measures only about 100 lines of source code. The main difference with micro-Max is that Fairy-Max loads its move-generator tables from a file, so that the rules for piece movement can be easily configured to implement unorthodox pieces. Fairy-Max can therefore play a large number of variants, normal Chess being one of those. In addition it plays Knightmate, Capablanca and Gothic Chess, Shatranj, Courier Chess, Cylinder chess, Berolina Chess, while the user can easily define new variants. It can be obtained from:



HoiChess is a not-so-very-strong Chess engine, which comes with a derivative HoiXiangqi, able to play Chinese Chess. It can be obtained from the standard Linux repositories through:

sudo apt-get install hoichess


Crafty is a chess engine written by Bob Hyatt. You can use XBoard to play a game against Crafty, hook Crafty up to an ICS, or use Crafty to interactively analyze games and positions for you.

Crafty is a strong, rapidly evolving chess program. This rapid pace of development is good, because it means Crafty is always getting better.  This can sometimes cause problems with backwards compatibility, but usually the latest version of Crafty will work well with the latest version of XBoard. Crafty can be obtained from its author's FTP site: ftp://ftp.cis.uab.edu/hyatt/.

To use Crafty with XBoard, give the -fcp and -fd options as follows, where <crafty's directory> is the directory in which you installed Crafty and placed its book and other support files.

Gnu General Public License

Copyright (C) 2007 Free Software Foundation, Inc. `http://fsf.org/'

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.

The GNU General Public License is a free, copyleft license for software and other kinds of works.

The licenses for most software and other practical works are designed to take away your freedom to share and change the works.  By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program -- to make sure it remains free software for all its users.  We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors.  You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price.  Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for them if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you these rights or asking you to surrender the rights.  Therefore, you have certain responsibilities if you distribute copies of the software, or if you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received.  You must make sure that they, too, receive or can get the source code.  And you must show them these terms so they know their rights.

Developers that use the GNU GPL protect your rights with two steps: (1) assert copyright on the software, and (2) offer you this License giving you legal permission to copy, distribute and/or modify it.

For the developers' and authors' protection, the GPL clearly explains that there is no warranty for this free software.  For both users' and authors' sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions.

Some devices are designed to deny users access to install or run modified versions of the software inside them, although the manufacturer can do so.  This is fundamentally incompatible with the aim of protecting users' freedom to change the software.  The systematic pattern of such abuse occurs in the area of products for individuals to use, which is precisely where it is most unacceptable. Therefore, we have designed this version of the GPL to prohibit the practice for those products.  If such problems arise substantially in other domains, we stand ready to extend this provision to those domains in future versions of the GPL, as needed to protect the freedom of users.

Finally, every program is threatened constantly by software patents. States should not allow patents to restrict development and use of software on general-purpose computers, but in those that do, we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary.  To prevent this, the GPL assures that patents cannot be used to render the program non-free.

The precise terms and conditions for copying, distribution and modification follow.


“This License” refers to version 3 of the GNU General Public License.

“Copyright” also means copyright-like laws that apply to other kinds of works, such as semiconductor masks.

“The Program” refers to any copyrightable work licensed under this License.  Each licensee is addressed as “you”.  “Licensees” and “recipients” may be individuals or organizations.

To “modify” a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission, other than the making of an exact copy.  The resulting work is called a “modified version” of the earlier work or a work “based on” the earlier work.

A “covered work” means either the unmodified Program or a work based on the Program.

To “propagate” a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy.  Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.

To “convey” a work means any kind of propagation that enables other parties to make or receive copies.  Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.

An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License.  If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.

Source Code.

The “source code” for a work means the preferred form of the work for making modifications to it.  “Object code” means any non-source form of a work.

A “Standard Interface” means an interface that either is an official standard defined by a recognized standards body, or, in the case of interfaces specified for a particular programming language, one that is widely used among developers working in that language.

The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component, and (b) serves only to enable use of the work with that Major Component, or to implement a Standard Interface for which an implementation is available to the public in source code form.  A “Major Component”, in this context, means a major essential component (kernel, window system, and so on) of the specific operating system (if any) on which the executable work runs, or a compiler used to produce the work, or an object code interpreter used to run it.

The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities.  However, it does not include the work's System Libraries, or general-purpose tools or generally available free programs which are used unmodified in performing those activities but which are not part of the work.  For example, Corresponding Source includes interface definition files associated with source files for the work, and the source code for shared libraries and dynamically linked subprograms that the work is specifically designed to require, such as by intimate data communication or control flow between those subprograms and other parts of the work.

The Corresponding Source need not include anything that users can regenerate automatically from other parts of the Corresponding Source.

The Corresponding Source for a work in source code form is that same work.

Basic Permissions.

All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met.  This License explicitly affirms your unlimited permission to run the unmodified Program.  The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work.  This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.

You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright.  Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.

Conveying under any other circumstances is permitted solely under the conditions stated below.  Sublicensing is not allowed; section 10 makes it unnecessary.

Protecting Users' Legal Rights From Anti-Circumvention Law.

No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention of such measures.

When you convey a covered work, you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work, and you disclaim any intention to limit operation or modification of the work as a means of enforcing, against the work's users, your or third parties' legal rights to forbid circumvention of technological measures.

Conveying Verbatim Copies.

You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.

You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.

Conveying Modified Source Versions.

You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:

The work must carry prominent notices stating that you modified it, and giving a relevant date.

The work must carry prominent notices stating that it is released under this License and any conditions added under section 7.  This requirement modifies the requirement in section 4 to “keep intact all notices”.

You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy.  This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged.  This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.

If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.

A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit.  Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

Conveying Non-Source Forms.

You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:

Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.

Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.

Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source.  This alternative is allowed only occasionally and noncommercially, and only if you received the object code with such an offer, in accord with subsection 6b.

Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge.  You need not require recipients to copy the Corresponding Source along with the object code.  If the place to copy the object code is a network server, the Corresponding Source may be on a different server (operated by you or a third party) that supports equivalent copying facilities, provided you maintain clear directions next to the object code saying where to find the Corresponding Source. Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements.

Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d.

A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work.

A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling.  In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage.  For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product.  A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.

“Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source.  The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.

If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information.  But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).

The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed.  Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.

Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.

Additional Terms.

“Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law.  If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.

When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it.  (Additional permissions may be written to require their own removal in certain cases when you modify the work.)  You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.

Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:

Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or

Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or

Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or

Limiting the use for publicity purposes of names of licensors or authors of the material; or

Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or

Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.

All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10.  If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term.  If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.

If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.

Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.


You may not propagate or modify a covered work except as expressly provided under this License.  Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License.  If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.

Acceptance Not Required for Having Copies.

You are not required to accept this License in order to receive or run a copy of the Program.  Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance.  However, nothing other than this License grants you permission to propagate or modify any covered work.  These actions infringe copyright if you do not accept this License.  Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

Automatic Licensing of Downstream Recipients.

Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License.  You are not responsible for enforcing compliance by third parties with this License.

An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations.  If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.

You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License.  For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.


A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based.  The work thus licensed is called the contributor's “contributor version”.

A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version.  For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.

Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.

In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement).  To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.

If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients.  “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.

If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.

A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License.  You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.

Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.

No Surrender of Others' Freedom.

If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License.  If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all.  For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.

Use with the GNU Affero General Public License.

Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work.  The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.

Revised Versions of this License.

The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time.  Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number.  If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation.  If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

Later license versions may give you additional or different permissions.  However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.

Disclaimer of Warranty.


Limitation of Liability.


Interpretation of Sections 15 and 16.

If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program.  It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.


This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see `http://www.gnu.org/licenses/'.

Also add information on how to contact you by electronic and paper mail.

If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:

This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License.  Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.

You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see `http://www.gnu.org/licenses/'.

The GNU General Public License does not permit incorporating your program into proprietary programs.  If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library.  If this is what you want to do, use the GNU Lesser General Public License instead of this License.  But first, please read `http://www.gnu.org/philosophy/why-not-lgpl.html'.

Referenced By


$Date: GNU