foot.ini - Man Page

configuration file for foot(1)


foot uses the standard unix configuration format, with section based key/value pairs. The default section is usually unnamed, i.e. not prefixed with a [section]. However it can also be explicitly named [main], say if it needs to be reopened after any of the other sections.

foot will search for a configuration file in the following locations, in this order:

  • XDG_CONFIG_HOME/foot/foot.ini
  • ~/.config/foot/foot.ini
  • XDG_CONFIG_DIRS/foot/foot.ini



Executable to launch. Typically a shell. Default: $SHELL if set, otherwise the user's default shell (as specified in /etc/passwd). You can also pass arguments. For example /bin/bash --norc.


Boolean. If enabled, the shell will be launched as a login shell, by prepending a '-' to argv[0]. Default: no.


Value to set the environment variable TERM to. Default: foot

font,  font-bold,  font-italic,  font-bold-italic

Comma separated list of fonts to use, in fontconfig format. That is, a font name followed by a list of colon-separated options. Most noteworthy is :size=n, which is used to set the font size. Note that the font size is also affected by the dpi-aware option.

  • Dina:weight=bold:slant=italic
  • Courier New:size=12
  • Fantasque Sans Mono:fontfeatures=ss01

For each option, the first font is the primary font. The remaining fonts are fallback fonts that will be used whenever a glyph cannot be found in the primary font.

The fallback fonts are searched in the order they appear. If a glyph cannot be found in any of the fallback fonts, the dynamic fallback list from fontconfig (for the primary font) is searched.

font-bold, font-italic and font-bold-italic allow custom fonts to be used for bold/italic/bold+italic fonts. If left unconfigured, the bold/italic variants of the regular font(s) specified in font are used. Note: you may have to tweak the size(s) of the custom bold/italic fonts to match the regular font.

To disable bold and/or italic fonts, set e.g. font-bold to exactly the same value as font.

Default: monospace:size=8 (font), not set (font-bold, font-italic, font-bold-italic).


Absolute path to configuration file to import.

The import file has its own section scope. I.e. the including configuration is still in the default section after the include, regardless of which section the included file ends in.

  • The path must be an absolute path, or start with ~/.
  • Multiple include directives are allowed, but only one path per directive.
  • Nested imports are allowed.

Default: not set.


An absolute value, in points, that override line height from the font metrics.

You can specify a height in pixels by using the px suffix: e.g. line-height=12px.

See also: vertical-letter-offset.

Default: not set.


Spacing between letters, in points. A positive value will increase the cell size, and a negative value shrinks it.

You can specify a letter spacing in pixels by using the px suffix: e.g. letter-spacing=2px.

See also: horizontal-letter-offset.

Default: 0.

horizontal-letter-offset,  vertical-letter-offset

Configure the horizontal and vertical offsets used when positioning glyphs within cells, in points, relative to the top left corner.

To specify an offset in pixels, append px: e.g. horizontal-letter-offset=2px.

Default: 0.


Use a custom offset for underlines. The offset is, by default, in points and relative the font's baseline. A positive value positions the underline under the baseline, while a negative value positions it above the baseline.

To specify an offset in pixels, append px: underline-offset=2px.

If left unset (the default), the offset specified in the font is used, or estimated by foot if the font lacks underline positioning information.

Default: unset.

box-drawings-uses-font-glyphs Boolean. When disabled, foot generates

box/line drawing characters itself. The are several advantages to doing this instead of using font glyphs:

  • No antialiasing effects where e.g. line endpoints appear dimmed down, or blurred.
  • Line- and box characters are guaranteed to span the entire cell, resulting in a gap-less appearance.
  • No alignment issues, i.e. lines are centered when they should be.
  • Many fonts lack some, or all, of the line- and box drawing characters, causing fallback fonts to be used, which results in out-of-place looking glyphs (for example, badly sized).

When enabled, box/line drawing characters are rendered using font glyphs. This may result in a more uniform look, in some use cases.

Default: no.


auto, yes, or no.

When set to yes, fonts are sized using the monitor's DPI, making a font of a given size have the same physical size, regardless of monitor. In other words, if you drag a foot window between different monitors, the font size remains the same.

In this mode, the monitor's scaling factor is ignored; doubling the scaling factor will not double the font size.

When set to no, the monitor's DPI is ignored. The font is instead sized using the monitor's scaling factor; doubling the scaling factor does double the font size.

Finally, if set to auto, fonts will be sized using the monitor's DPI if all monitors have a scaling factor of 1. If at least one monitor as a scaling factor larger than 1 (regardless of whether the foot window is mapped on that monitor or not), fonts will be scaled using the scaling factor.

Note that this option typically does not work with bitmap fonts, which only contains a pre-defined set of sizes, and cannot be dynamically scaled. Whichever size (of the available ones) that best matches the DPI or scaling factor, will be used.

Also note that if the font size has been specified in pixels (:pixelsize=N, instead of :size=N), DPI scaling (dpi-aware=yes) will have no effect (the specified pixel size will be used as is). But, if the monitor's scaling factor is used to size the font (dpi-aware=no), the font's pixel size will be multiplied with the scaling factor.

Default: auto


Padding between border and glyphs, in pixels (subject to output scaling), on the form XxY.

This will add at least X pixels on both the left and right sides, and Y pixels on the top and bottom sides. The grid content will be anchored in the top left corner. I.e. if the window manager forces an odd window size on foot, the additional pixels will be added to the right and bottom sides.

To instead center the grid content, append center (e.g. pad=5x5 center).

Default: 2x2.


Time, in milliseconds, of "idle time" before foot sends the new window dimensions to the client application while doing an interactive resize of a foot window. Idle time in this context is a period of time where the window size is not changing.

In other words, while you are fiddling with the window size, foot does not send the updated dimensions to the client. Only when you pause the fiddling for resize-delay-ms milliseconds is the client updated.

Emphasis is on while here; as soon as the interactive resize ends (i.e. when you let go of the window border), the final dimensions is sent to the client, without any delays.

Setting it to 0 disables the delay completely.

Default: 100.


Initial window width and height in pixels (subject to output scaling), on the form WIDTHxHEIGHT. The height includes the titlebar when using CSDs. Mutually exclusive to initial-window-size-chars. Default: 700x500.


Initial window width and height in characters, on the form WIDTHxHEIGHT. Mutually exclusive to initial-window-size-pixels.'

Note that if you have a multi-monitor setup, with different scaling factors, there is a possibility the window size will not be set correctly. If that is the case, use initial-window-size-pixels instead.

Default: not set.


Initial window mode for each newly spawned window: windowed, maximized or fullscreen. Default: windowed.


Initial window title. Default: foot.


Boolean. If enabled, applications are not allowed to change the title at run-time. Default: no.


Value to set the app-id property on the Wayland window to. The compositor can use this value to e.g. group multiple windows, or apply window management rules. Default: foot.


Semi-boolean. When enabled, bold text is rendered in a brighter color (in addition to using a bold font). The color is brightened by increasing its luminance.

If set to palette-based, rather than a simple yes|true, colors matching one of the 8 regular palette colors will be brightened using the corresponding bright palette color. Other colors will not be brightened.

Default: no.


String of characters that act as word delimiters when selecting text. Note that whitespace characters are always word delimiters, regardless of this setting. Default: ,│`|:"'()[]{}<>


Command to execute to display a notification. ${title} and ${body} will be replaced with the notification's actual title and body (message content).

${app-id} is replaced with the value of the command line option --app-id, and defaults to foot.

${window-title} is replaced with the current window title.

Applications can trigger notifications in the following ways:

  • OSC 777: \e]777;notify;<title>;<body>\e\\

By default, notifications are inhibited if the foot window has keyboard focus. See notify-focus-inhibit.

Default: notify-send -a ${app-id} -i ${app-id} ${title} ${body}.


Boolean. If enabled, foot will not display notifications if the terminal window has keyboard focus.

Default: yes


Clipboard target to automatically copy selected text to. One of none, primary, clipboard or both. Default: primary.


Number of threads to use for rendering. Set to 0 to disable multithreading. Default: the number of available logical CPUs (including SMT). Note that this is not always the best value. In some cases, the number of physical cores is better.



When set to yes, foot will signal urgency to the compositor through the XDG activation protocol whenever BEL is received, and the window does NOT have keyboard foccus.

If the compositor does not implement this protocol, the margins will be painted in red instead.

Applications can enable/disable this feature programmatically with the CSI ? 1042 h and CSI ? 1042 l escape sequences.

Default: no


When set to yes, foot will emit a desktop notification using the command specified in the notify option whenever BEL is received. By default, bell notifications are shown only when the window does not have keyboard focus. See notify-focus-inhibit.

Default: no


When set, foot will execute this command when BEL is received. Default: none


Whether to run the command on BEL even while focused. Default: no

SECTION: scrollback


Number of scrollback lines. The maximum number of allocated lines will be this value plus the number of visible lines, rounded up to the nearest power of 2. Default: 1000.


Amount to multiply mouse scrolling with. It is a decimal number, i.e. fractions are allowed. Default: 3.0.


Configures the style of the scrollback position indicator. One of none, fixed or relative. none disables the indicator completely. fixed always renders the indicator near the top of the window, and relative renders the indicator at the position corresponding to the current scrollback position. Default: relative.


Which format to use when displaying the scrollback position indicator. Either percentage, line, or a custom fixed string. This option is ignored if indicator-position=none. Default: empty string.



Command to execute when opening URLs. ${url} will be replaced with the actual URL. Default: xdg-open ${url}.


When to underline OSC-8 URLs. Possible values are url-mode and always.

When set to url-mode, OSC-8 URLs are only highlighted in URL mode, just like auto-detected URLs.

When set to always, OSC-8 URLs are always highlighted, regardless of their other attributes (bold, italic etc). Note that this does not make them clickable.

Default: url-mode


String of characters to use when generating key sequences for URL jump labels.

If you change this option to include the letter t, you should also change the default [url-bindings].toggle-url-visible key binding to avoid a clash.

Default: sadfjklewcmpgh.


Comma separated list of protocols (schemes) that should be recognized in URL mode. Note that only auto-detected URLs are affected by this option. OSC-8 URLs are always enabled, regardless of protocol. Default: http, https, ftp, ftps, file, gemini, gopher.


Set of characters allowed in auto-detected URLs. Any character not included in this set constitutes an URL delimiter.

Default: abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-_.,~:;/?#@!$&%*+="'.

SECTION: cursor

This section controls the cursor style and color. Note that applications can change these at runtime.


Configures the default cursor style, and is one of: block, beam or underline. Note that this can be overridden by applications. Default: block.


Boolean. Enables blinking cursor. Note that this can be overridden by applications. Default: no.


Two RRGGBB values (i.e. plain old 6-digit hex values, without prefix) specifying the foreground (text) and background (cursor) colors for the cursor.

Default: inversed foreground and background colors.

Note that this value only applies to the block cursor. The other cursor styles are always rendered with the foreground color.


Thickness (width) of the beam styled cursor. The value is in points, and its exact value thus depends on the monitor's DPI. To instead specify a thickness in pixels, use the px suffix: e.g. beam-thickness=2px. Default: 1.5


Thickness (height) of the underline styled cursor. The value is in points, and its exact value thus depends on the monitor's DPI.

To instead specify a thickness in pixels, use the px suffix: e.g. underline-thickness=2px.

Note that if left unset, the cursor's thickness will scale with the font size, while if set, the size is fixed.

Default: font underline thickness.

SECTION: mouse


Boolean. When enabled, the mouse cursor is hidden while typing. Default: no.


Boolean. This option controls the initial value for the alternate scroll mode. When this mode is enabled, mouse scroll events are translated to up/down key events when displaying the alternate screen.

This lets you scroll with the mouse in e.g. pagers (like less) without enabling native mouse support in them.

Alternate scrolling is not used if the application enables native mouse support.

This option can be modified by applications at run-time using the escape sequences CSI ? 1007 h (enable) and CSI ? 1007 l (disable).

Default: yes.

SECTION: colors

This section controls the 16 ANSI colors, the default foreground and background colors, and the extended 256 color palette. Note that applications can change these at runtime.

The colors are in RRGGBB format (i.e. plain old 6-digit hex values, without prefix). That is, they do not have an alpha component. You can configure the background transparency with the alpha option.


Default foreground color. This is the color used when no ANSI color is being used. Default: dcdccc.


Default background color. This is the color used when no ANSI color is being used. Default: 111111.

regular0,  regular1 .. regular7

The eight basic ANSI colors. Default: 222222, cc9393, 7f9f7f, d0bf8f, 6ca0a3, dc8cc3, 93e0e3 and dcdccc (a variant of the zenburn theme).

bright0,  bright1 .. bright7

The eight bright ANSI colors. Default: 666666, dca3a3, bfebbf, f0dfaf, 8cd0d3, fcace3, b3ffff and ffffff (a variant of the zenburn theme).

dim0,  dim1 .. dim7

Custom colors to use with dimmed colors. Dimmed colors do not have an entry in the color palette. Applications emit them by combining a color value, and a "dim" attribute.

By default, foot implements this by reducing the luminance of the current color. This is a generic approach that applies to both colors from the 256-color palette, as well as 24-bit RGB colors.

You can change this behavior by setting the dimN options. When set, foot will match the current color against the color palette, and if it matches one of the regularN colors, the corresponding dimN color will be used.

If instead the current color matches one of the brightN colors, the corresponding regularn color will be used.

If the current color does not match any known colors, it is dimmed by reducing the luminance (i.e. the same behavior as if the dimN options are unconfigured). 24-bit RGB colors will typically fall into this category.

Note that applications can change the regularN and brighN colors at runtime. However, they have no way of changing the dimN colors. If an application has changed the regularN colors, foot will still use the corresponding dimN color, as configured in foot.ini.

Default: not set.

0 .. 255

Arbitrary colors in the 256-color palette. Default: for 0 .. 15, see regular and bright defaults above; see for an explanation of the remainder.


Background translucency. A value in the range 0.0-1.0, where 0.0 means completely transparent, and 1.0 is opaque. Default: 1.0.

selection-foreground,  selection-background

Foreground (text) and background color to use in selected text. Note that both options must be set, or the default will be used. Default: inverse foreground/background.


To color values specifying the foreground (text) and background colors to use when rendering jump labels in URL mode. Default: regular0 regular3.


Two color values specifying the foreground (text) and background (indicator itself) colors for the scrollback indicator.

Default: first regular color (black) for foreground, and fifth bright color (light blue) for background.


Color to use for the underline used to highlight URLs in URL mode. Default: regular3.


This section controls the look of the CSDs (Client Side Decorations). Note that the default is to not use CSDs, but instead to use SSDs (Server Side Decorations) when the compositor supports it.

Note that unlike the colors defined in the colors section, the color values here are in AARRGGBB (i.e. plain old 8-digit hex values) format. I.e. they contain an alpha component - 00 means completely transparent, and ff fully opaque.

  • ffffffff: white, fully opaque
  • ff000000: black, fully opaque
  • 7fffffff: white, semi-transparent
  • ff00ff00: green, fully opaque

Which type of window decorations to prefer: client (CSD), server (SSD) or none.

Note that this is only a hint to the compositor. Depending on compositor support, and how it has been configured, it may instruct foot to use CSDs even though this option has been set to server, or render SSDs despite client or none being set.

Default: server.


Height, in pixels (subject to output scaling), of the titlebar. Default: 26.


Titlebar color. Default: use the default foreground color.


Font to use for the title bar. This is a list of fonts, similar to the main font option. Note that the font will be sized using the title bar size. That is, all :size and :pixelsize attributes will be ignored. Default: primary font.


Width of the border, in pixels (subject to output scaling). Note that the border encompasses the entire window, including the title bar. Default: 0.


Color of border. By default, the title bar color is used. If the title bar color has not been set, the default foreground color (from the color scheme) is used. Default: titlebar color.


Width, in pixels (subject to output scaling), of the minimize/maximize/close buttons. Default: 26.


Foreground color on the minimize/maximize/close buttons. Default: use the default background color.


Minimize button's background color. Default: use the default regular4 color (blue).


Maximize button's background color. Default: use the default regular2 color (green).


Close button's background color. Default: use the default regular1 color (red).

SECTION: key-bindings

This section lets you override the default key bindings.

The general format is action=combo1...comboN. That is, each action may have one or more key combinations, space separated. Each combination is on the form mod1+mod2+key. The names of the modifiers and the key must be valid XKB key names.

Note that if Shift is one of the modifiers, the key must not be in upper case. For example, Control+Shift+V will never trigger, but Control+Shift+v will.

Note that Alt is usually called Mod1.

xkbcli interactive-wayland can be useful for finding keysym names.

A key combination can only be mapped to one action. Lets say you want to bind Control+Shift+R to fullscreen. Since this is the default shortcut for search-start, you first need to unmap the default binding. This can be done by setting action=none; e.g. search-start=none.


All key combinations listed here will not be sent to the application. Default: not bound.


Scrolls up/back one page in history. Default: Shift+Page_Up.


Scrolls up/back half of a page in history. Default: not bound.


Scrolls up/back a single line in history. Default: not bound.


Scroll down/forward one page in history. Default: Shift+Page_Down.


Scroll down/forward half of a page in history. Default: not bound.


Scroll down/forward a single line in history. Default: not bound.


Copies the current selection into the clipboard. Default: Control+Shift+c.


Pastes from the clipboard. Default: Control+Shift+v.


Pastes from the primary selection. Default: Shift+Insert (also defined in mouse-bindings).


Starts a scrollback/history search. Default: Control+Shift+r.


Increases the font size by 0.5pt. Default: Control+plus Control+equal Control+KP_Add.


Decreases the font size by 0.5pt. Default: Control+minus Control+KP_Subtract.


Resets the font size to the default. Default: Control+0 Control+KP_0.


Spawns a new terminal. If the shell has been configured to emit the OSC 7 escape sequence, the new terminal will start in the current working directory. Default: Control+Shift+n.


Minimizes the window. Default: not bound.


Toggle the maximized state. Default: not bound.


Toggles the fullscreen state. Default: not bound.

pipe-visible,  pipe-scrollback,  pipe-selected

Pipes the currently visible text, the entire scrollback, or the currently selected text to an external tool. The syntax for this option is a bit special; the first part of the value is the command to execute enclosed in "[]", followed by the binding(s).

You can configure multiple pipes as long as the command strings are different and the key bindings are unique.

Note that the command is not automatically run inside a shell; use sh -c "command line" if you need that.


pipe-visible=[sh -c "xurls | uniq | tac | fuzzel | xargs -r firefox"] Control+Print

Default: not bound


Enter URL mode, where all currently visible URLs are tagged with a jump label with a key sequence that will open the URL. Default: Control+Shift+u.


Enter URL mode, where all currently visible URLs are tagged with a jump label with a key sequence that will place the URL in the clipboard. Default: none.

SECTION: search-bindings

This section lets you override the default key bindings used in scrollback search mode. The syntax is exactly the same as the regular key-bindings.


Aborts the search. The viewport is restored and the primary selection is not updated. Default: Control+g Control+c Escape.


Exit search mode and copy current selection into the primary selection. Viewport is not restored. To copy the selection to the regular clipboard, use Control+Shift+c. Default: Return.


Search backwards in the scrollback history for the next match. Default: Control+r.


Searches forwards in the scrollback history for the next match. Default: Control+s.


Moves the cursor in the search box one character to the left. Default: Left Control+b.


Moves the cursor in the search box one word to the left. Default: Control+Left Mod1+b.


Moves the cursor in the search box one character to the right. Default: Right Control+f.


Moves the cursor in the search box one word to the right. Default: Control+Right Mod1+f.


Moves the cursor in the search box to the beginning of the input. Default: Home Control+a.


Moves the cursor in the search box to the end of the input. Default: End Control+e.


Deletes the character before the cursor. Default: BackSpace.


Deletes the word before the cursor. Default: Mod1+BackSpace Control+BackSpace.


Deletes the character after the cursor. Default: Delete.


Deletes the word after the cursor. Default: Mod1+d Control+Delete.


Extend current selection to the next word boundary. Default: Control+w.


Extend the current selection to the next whitespace. Default: Control+Shift+w.


Paste from the clipboard into the search buffer. Default: Control+v Control+y.


Paste from the primary selection into the search buffer. Default: Shift+Insert.

SECTION: url-bindings

This section lets you override the default key bindings used in URL mode. The syntax is exactly the same as the regular key-bindings.

Be careful; do not use single-letter keys that are also used in [url].label-letters, as doing so will make some URLs inaccessible.


Exits URL mode without opening an URL. Default: Control+g Control+c Control+d Escape.


By default, the jump label only shows the key sequence required to activate it. This is fine as long as the URL is visible in the original text.

But with e.g. OSC-8 URLs (the terminal version of HTML anchors, i.e. "links"), the text on the screen can be something completey different than the URL.

This action toggles between showing and hiding the URL on the jump label.

Default: t.

SECTION: mouse-bindings

This section lets you override the default mouse bindings.

The general format is action=combo1...comboN. That is, each action may have one or more key combinations, space separated. Each combination is on the form mod1+mod2+BTN_<name>[-COUNT]. The names of the modifiers must be valid XKB key names, and the button name must be a valid libinput name. You can find the button names using libinput debug-events.

Note that Shift cannot be used as a modifier in mouse bindings since it is used to enable selection when the client application is grabbing the mouse.

The trailing COUNT is optional and specifies the click count required to trigger the binding. The default if COUNT is omitted is 1.

A modifier+button combination can only be mapped to one action. Lets say you want to bind BTN_MIDDLE to fullscreen. Since BTN_MIDDLE is the default binding for primary-paste, you first need to unmap the default binding. This can be done by setting action=none; e.g. primary-paste=none.

All actions listed under key-bindings can be used here as well.


Begin an interactive selection. The selection is finalized, and copied to the primary selection, when the button is released. Default: BTN_LEFT.


Begin an interactive block selection. The selection is finalized, and copied to the primary selection, when the button is released. Default: Control+BTN_LEFT.


Begin an interactive word-wise selection, where words are separated by whitespace and all characters defined by the word-delimiters option. The selection is finalized, and copied to the primary selection, when the button is released. Default: BTN_LEFT-2.


Same as select-word, but the characters in the word-delimiters option are ignored. I.e only whitespace characters act as delimiters. The selection is finalized, and copied to the primary selection, when the button is released. Default: Control+_BTN_LEFT-2.


Begin an interactive row-wise selection. The selection is finalized, and copied to the primary selection, when the button is released. Default: BTN_LEFT-3.


Interactively extend an existing selection, using the original selection mode (normal, block, word-wise or row-wise). The selection is finalized, and copied to the primary selection, when the button is released. Default: BTN_RIGHT.


Same as select-extend, but forces the selection mode to normal (i.e. character wise). Note that this causes subsequent select-extend operations to be character wise. This action is ignored for block selections. Default: Control+BTN_RIGHT.


Pastes from the primary selection. Default: BTN_MIDDLE.


This section is for advanced users and describes configuration options that can be used to tweak foot's low-level behavior.

These options are not included in the example configuration. You should not change these unless you understand what they do.

Note that these options may change, or be removed at any time, without prior notice.

When reporting bugs, please mention if, and to what, you have changed any of these options.


Overrides the default scaling filter used when down-scaling bitmap fonts (e.g. emoji fonts). Possible values are none, nearest, bilinear, cubic or lanczos3. cubic and lanczos3 produce the best results, but are slower (with lanczos3 being the best and slowest).

Default: lanczos3.


Boolean. When enabled, glyphs wider than their cell(s) are allowed to render into one additional neighbouring cell.

One use case for this are fonts with wide italic characters that "bend" into the next cell. Without this option, such glyphs will appear "cut off".

Another use case are fonts with "icon" characters in the Unicode private usage area, e.g. Nerd Fonts, or Powerline Fonts and legacy emoji characters like WHITE FROWNING FACE.

Note: might impact performance depending on the font used. Especially small font sizes can cause many overflowing glyphs because of subpixel rendering.

Default: yes.


Enables a frame rendering timer, that prints the time it takes to render each frame, in microseconds, either on-screen, to stderr, or both. Valid values are none, osd, log and both. Default: none.


Line thickness to use for LIGHT box drawing line characters, in points. This value is converted to pixels using the monitor's DPI, and then multiplied with the cell size. The end result is that a larger font (and thus larger cells) result in thicker lines. Default: 0.04.


Boolean. When enabled, box drawing "shades" (e.g. LIGHT SHADE, MEDIUM SHADE and DARK SHADE) are rendered as solid blocks using a darker variant of the current foreground color.

When disabled, they are instead rendered as checker box pattern, using the current foreground color as is.

Default: yes.

delayed-render-lower,  delayed-render-upper

These two values control the timeouts (in nanoseconds) that are used to mitigate screen flicker caused by clients writing large, non-atomic screen updates.

If a client splits up a screen update over multiple write(3) calls, we may end up rendering an intermediate frame, quickly followed by another frame with the final screen content. For example, the client may erase part of the screen (or scroll) in one write, and then write new content in one or more subsequent writes. Rendering the frame when the screen has been erased, but not yet filled with new content will be perceived as screen flicker.

The real solution to this is Application Synchronized Updates (

The problem with this is twofold - first, it has not yet been standardized, and thus there are not many terminal emulators that implement it (foot does implement it), and second, applications must be patched to use it.

Until this has happened, foot offers an interim workaround; an attempt to mitigate the screen flicker without affecting neither performance nor latency.

It is based on the fact that the screen is updated at a fixed interval (typically 60Hz). For us, this means it does not matter if we render a new frame at the beginning of a frame interval, or at the end. Thus, the goal is to introduce a delay between receiving client data and rendering the resulting state, but without causing a frame skip.

While it should be possible to estimate the amount of time left until the next frame, foot's algorithm is currently not that advanced, but is based on statistics I guess you could say - the delay we introduce is so small that the risk of pushing the frame over to the next frame interval is also very small.

Now, that was a lot of text. But what is it foot actually does?

When receiving client data, it schedules a timer, the delayed-render-lower. If we do not receive any more client data before the timer has run out, we render the frame. If however, we do receive more data, the timer is re-scheduled. That is, each time we receive client data, frame rendering is delayed another delayed-render-lower nanoseconds.

Now, while this works very well with most clients, it would be possible to construct a malicious client that keeps writing data at a slow pace. To the user, this would look like foot has frozen as we never get to render a new frame. To prevent this, an upper limit is set - delayed-render-upper. If this timer runs out, we render the frame regardless of what the client is doing.

If changing these values, note that the lower timeout must be set lower than the upper timeout, but that this is not verified by foot. Furthermore, both values must be less than 16ms (that is, 16000000 nanoseconds).

You can disable the feature altogether by setting either value to 0. In this case, frames are rendered "as soon as possible".

Default: lower=500000 (0.5ms), upper=8333333 (8.3ms - half a frame interval).


Boolean. When enabled, foot will 'damage' the entire window each time a frame has been rendered. This forces the compositor to redraw the entire window. If disabled, foot will only 'damage' updated rows.

There is normally no reason to enable this. However, it has been seen to workaround an issue with fractional scaling in Gnome.

Note that enabling this option is likely to increase CPU and/or GPU usage (by the compositor, not by foot), and may have a negative impact on battery life.

Default: no.


Boolean. When enabled, foot will use utf8proc to do grapheme cluster segmentation while parsing "printed" text. Then, when rendering, it will use fcft (if compiled with HarfBuzz support) to shape the grapheme clusters.

This is required to render e.g. flag (emoji) sequences, keycap sequences, modifier sequences, zero-width-joiner (ZWJ) sequences and emoji tag sequences. It might also improve rendering of composed characters, depending on font.

  • foot must have been compiled with utf8proc support
  • fcft must have been compiled with HarfBuzz support

See also: grapheme-width-method.

Default: yes


Selects which method to use when calculating the width (i.e. number of columns) of a grapheme cluster. One of double-width and wcswidth.

wcswidth simply adds together the individual width of all codepoints making up the cluster.

double-width does the same, but limits the maximum number of columns to 2. This is more correct, but may break some applications since applications typically use wcswidth(3) internally to calculate the width. This results in cursor de-synchronization issues.

Default: wcswidth


Boolean. When enabled, foot will use heuristics to try to verify the primary font is a monospace font, and warn if it is not.

Disable this if you still want to use the font, even if foot thinks it is not monospaced.

You may also want to disable it to get slightly faster startup times.

Default: yes


This option controls the amount of virtual address space used by the pixmap memory to which the terminal screen content is rendered.

It does not change how much physical memory foot uses.

Foot uses a memory mapping trick to implement fast rendering of interactive scrolling (typically, but applies to "slow" scrolling in general). Example: holding down the 'up' or 'down' arrow key to scroll in a text editor.

For this to work, it needs a large amount of virtual address space. Again, note that this is not physical memory.

On a normal x64 based computer, each process has 128TB of virtual address space, and newer ones have 64PB. This is an insane amount and most applications do not use anywhere near that amount.

Each foot terminal window can allocate up to 2GB of virtual address space. With 128TB of address space, that means a maximum of 65536 windows in server/daemon mode (for 2GB). That should be enough, yes?

However, the Wayland compositor also needs to allocate the same amount of virtual address space. Thus, it has a slightly higher chance of running out of address space since it needs to host all running Wayland clients in the same way, at the same time.

In the off chance that this becomes a problem for you, you can reduce the amount used with this option.

Or, for optimal performance, you can increase it to the maximum allowed value, 2GB (but note that you most likely will not notice any difference compared to the default value).

Setting it to 0 disables the feature.

  • only supported on 64-bit architectures
  • only supported on Linux

Default: 512. Maximum allowed: 2048 (2GB).

See Also

foot(1), footclient(1)

Referenced By

foot(1), footclient(1), foot-ctlseqs(7).