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picom - Man Page

a compositor for X11

Examples (TL;DR)


picom [Options]


picom is a compositor based on Dana Jansens' version of xcompmgr (which itself was written by Keith Packard). It includes some improvements over the original xcompmgr, like window frame opacity and inactive window transparency.


-h,  --help

Get the usage text embedded in program code, which may be more up-to-date than this man page.

-r,  --shadow-radius=RADIUS

The blur radius for shadows, in pixels. (defaults to 12)

-o,  --shadow-opacity=OPACITY

The opacity of shadows. (0.0 - 1.0, defaults to 0.75)

-l,  --shadow-offset-x=OFFSET

The left offset for shadows, in pixels. (defaults to -15)

-t,  --shadow-offset-y=OFFSET

The top offset for shadows, in pixels. (defaults to -15)

-I,  --fade-in-step=OPACITY_STEP

Opacity change between steps while fading in. (0.01 - 1.0, defaults to 0.028)

-O,  --fade-out-step=OPACITY_STEP

Opacity change between steps while fading out. (0.01 - 1.0, defaults to 0.03)

-D,  --fade-delta=MILLISECONDS

The time between steps in fade step, in milliseconds. (> 0, defaults to 10)

-c,  --shadow

Enabled client-side shadows on windows. Note desktop windows (windows with _NET_WM_WINDOW_TYPE_DESKTOP) never get shadow, unless explicitly requested using the wintypes option.

-f,  --fading

Fade windows in/out when opening/closing and when opacity changes, unless --no-fading-openclose is used.


Equals to -f. Deprecated.

-i,  --inactive-opacity=OPACITY

Opacity of inactive windows. (0.1 - 1.0, defaults to 1.0)

-e,  --frame-opacity=OPACITY

Opacity of window titlebars and borders. (0.1 - 1.0, disabled by default)

-b,  --daemon

Daemonize process. Fork to background after initialization. This option can only be set from the command line, setting this in the configuration file will have no effect.


Set the log level. Possible values are "TRACE", "DEBUG", "INFO", "WARN", "ERROR", in increasing level of importance. Case doesn’t matter. If using the "TRACE" log level, it’s better to log into a file using --log-file, since it can generate a huge stream of logs.


Set the log file. If --log-file is never specified, logs will be written to stderr. Otherwise, logs will to written to the given file, though some of the early logs might still be written to the stderr. When setting this option from the config file, it is recommended to use an absolute path.


Use the old version of the backends. This option can not be set from the config file.


Show all X errors (for debugging).

--config PATH

Look for configuration file at the path. See Configuration Files section below for where picom looks for a configuration file by default. Use /dev/null to avoid loading configuration file.

--write-pid-path PATH

Write process ID to a file. it is recommended to use an absolute path.

--shadow-color STRING

Color of shadow, as a hex string (#000000)

--shadow-red VALUE

Red color value of shadow (0.0 - 1.0, defaults to 0).

--shadow-green VALUE

Green color value of shadow (0.0 - 1.0, defaults to 0).

--shadow-blue VALUE

Blue color value of shadow (0.0 - 1.0, defaults to 0).


Let inactive opacity set by -i override the _NET_WM_WINDOW_OPACITY values of windows.

--active-opacity OPACITY

Default opacity for active windows. (0.0 - 1.0, defaults to 1.0)

--inactive-dim VALUE

Dim inactive windows. (0.0 - 1.0, defaults to 0.0)

--corner-radius VALUE

Sets the radius of rounded window corners. When > 0, the compositor will round the corners of windows. Does not interact well with --transparent-clipping. (defaults to 0).

--corner-radius-rules RADIUS:'CONDITION'

Specify a list of corner radius rules. Overrides the corner radii of matching windows. This option takes precedence over the --rounded-corners-exclude option, and also overrides the default exclusion of fullscreen windows. The condition has the same format as --opacity-rule.

--rounded-corners-exclude CONDITION

Exclude conditions for rounded corners.


Disable vsync-aware frame pacing. By default, the compositor tries to make sure it only renders once per vblank interval, and also the render happens as late as possible to minimize the latency from updates to the screen. However this can sometimes cause stuttering, or even lowered frame rate. This option can be used to disable frame pacing.


Try to detect WM windows (a non-override-redirect window with no child that has WM_STATE) and mark them as active.


Mark override-redirect windows that doesn’t have a child window with WM_STATE focused.


Do not fade on window open/close.


Do not fade destroyed ARGB windows with WM frame. Workaround of bugs in Openbox, Fluxbox, etc.


Do not paint shadows on shaped windows. Note shaped windows here means windows setting its shape through X Shape extension. Those using ARGB background is beyond our control. Deprecated, use --shadow-exclude 'bounding_shaped' or --shadow-exclude 'bounding_shaped && !rounded_corners' instead.


Try to detect windows with rounded corners and don’t consider them shaped windows. The accuracy is not very high, unfortunately.


Detect _NET_WM_WINDOW_OPACITY on client windows, useful for window managers not passing _NET_WM_WINDOW_OPACITY of client windows to frame windows.

--vsync,  --no-vsync

Enable/disable VSync.


Use EWMH _NET_ACTIVE_WINDOW to determine currently focused window, rather than listening to FocusIn/FocusOut event. Might have more accuracy, provided that the WM supports it.


Unredirect all windows in some cases. Known to cause flickering when redirecting/unredirecting windows. Currently, unredirecting is triggered by following conditions:

  • If the top level window is taking up the entire screen. In multi-monitor setup, this means ALL monitors.
  • If there is no window.
  • If a window is fullscreen according to its WM hints. (can be disabled with --no-ewmh-fullscreen).
  • If a window requests to bypass the compositor (_NET_WM_BYPASS_COMPOSITOR). Windows are also unredirected unconditionally when monitors are powered off, regardless if --unredir-if-possible is set.
--unredir-if-possible-delay MILLISECONDS

Delay before unredirecting the window, in milliseconds. Defaults to 0.

--unredir-if-possible-exclude CONDITION

Conditions of windows that shouldn’t be considered full-screen for unredirecting screen.

--shadow-exclude CONDITION

Specify a list of conditions of windows that should have no shadow.

--clip-shadow-above CONDITION

Specify a list of conditions of windows that should have no shadow painted over, such as a dock window.

--fade-exclude CONDITION

Specify a list of conditions of windows that should not be faded.

--focus-exclude CONDITION

Specify a list of conditions of windows that should always be considered focused.


Use fixed inactive dim value, instead of adjusting according to window opacity.


Use WM_TRANSIENT_FOR to group windows, and consider windows in the same group focused at the same time.


Use WM_CLIENT_LEADER to group windows, and consider windows in the same group focused at the same time. This usually means windows from the same application will be considered focused or unfocused at the same time.WM_TRANSIENT_FOR has higher priority if --detect-transient is enabled, too.

--blur-method,  --blur-size,  --blur-deviation,  --blur-strength

Parameters for background blurring, see the Blur section for more information.


Blur background of semi-transparent / ARGB windows. Bad in performance, with driver-dependent behavior. The name of the switch may change without prior notifications.


Blur background of windows when the window frame is not opaque. Implies --blur-background. Bad in performance, with driver-dependent behavior. The name may change.


Use fixed blur strength rather than adjusting according to window opacity.

--blur-kern MATRIX

Specify the blur convolution kernel, with the following format:


In other words, the matrix is formatted as a list of comma separated numbers. The first two numbers must be integers, which specify the width and height of the matrix. They must be odd numbers. Then, the following width * height - 1 numbers specifies the numbers in the matrix, row by row, excluding the center element.

The elements are finite floating point numbers. The decimal pointer has to be . (a period), scientific notation is not supported.

The element in the center will either be 1.0 or varying based on opacity, depending on whether you have --blur-background-fixed. Yet the automatic adjustment of blur factor may not work well with a custom blur kernel.

A 7x7 Gaussian blur kernel (sigma = 0.84089642) looks like:

--blur-kern '7,7,0.000003,0.000102,0.000849,0.001723,0.000849,0.000102,0.000003,0.000102,0.003494,0.029143,0.059106,0.029143,0.003494,0.000102,0.000849,0.029143,0.243117,0.493069,0.243117,0.029143,0.000849,0.001723,0.059106,0.493069,0.493069,0.059106,0.001723,0.000849,0.029143,0.243117,0.493069,0.243117,0.029143,0.000849,0.000102,0.003494,0.029143,0.059106,0.029143,0.003494,0.000102,0.000003,0.000102,0.000849,0.001723,0.000849,0.000102,0.000003'

May also be one of the predefined kernels: 3x3box (default), 5x5box, 7x7box, 3x3gaussian, 5x5gaussian, 7x7gaussian, 9x9gaussian, 11x11gaussian. All Gaussian kernels are generated with sigma = 0.84089642 . If you find yourself needing to generate custom blur kernels, you might want to try the new blur configuration (See Blur).

--blur-background-exclude CONDITION

Exclude conditions for background blur.

--resize-damage INTEGER

Resize damaged region by a specific number of pixels. A positive value enlarges it while a negative one shrinks it. If the value is positive, those additional pixels will not be actually painted to screen, only used in blur calculation, and such. (Due to technical limitations, with --use-damage, those pixels will still be incorrectly painted to screen.) Primarily used to fix the line corruption issues of blur, in which case you should use the blur radius value here (e.g. with a 3x3 kernel, you should use --resize-damage 1, with a 5x5 one you use --resize-damage 2, and so on). May or may not work with --glx-no-stencil. Shrinking doesn’t function correctly.

--invert-color-include CONDITION

Specify a list of conditions of windows that should be painted with inverted color. Resource-hogging, and is not well tested.

--opacity-rule OPACITY:'CONDITION'

Specify a list of opacity rules, in the format PERCENT:PATTERN, like 50:name *= "Firefox". picom-trans is recommended over this. Note we don’t make any guarantee about possible conflicts with other programs that set _NET_WM_WINDOW_OPACITY on frame or client windows.

--shadow-exclude-reg GEOMETRY

Specify a X geometry that describes the region in which shadow should not be painted in, such as a dock window region. Use --shadow-exclude-reg x10+0-0, for example, if the 10 pixels on the bottom of the screen should not have shadows painted on.


Crop shadow of a window fully on a particular monitor to that monitor. This is currently implemented using the X RandR extension.

--backend BACKEND

Specify the backend to use: xrender, glx, or xr_glx_hybrid. xrender is the default one.

  • xrender backend performs all rendering operations with X Render extension. It is what xcompmgr uses, and is generally a safe fallback when you encounter rendering artifacts or instability.
  • glx (OpenGL) backend performs all rendering operations with OpenGL. It is more friendly to some VSync methods, and has significantly superior performance on color inversion (--invert-color-include) or blur (--blur-background). It requires proper OpenGL 2.0 support from your driver and hardware. You may wish to look at the GLX performance optimization options below. --xrender-sync-fence might be needed on some systems to avoid delay in changes of screen contents.
  • xr_glx_hybrid backend renders the updated screen contents with X Render and presents it on the screen with GLX. It attempts to address the rendering issues some users encountered with GLX backend and enables the better VSync of GLX backends. --vsync-use-glfinish might fix some rendering issues with this backend.

GLX backend: Avoid using stencil buffer, useful if you don’t have a stencil buffer. Might cause incorrect opacity when rendering transparent content (but never practically happened) and may not work with --blur-background. My tests show a 15% performance boost. Recommended.


GLX backend: Avoid rebinding pixmap on window damage. Probably could improve performance on rapid window content changes, but is known to break things on some drivers (LLVMpipe, xf86-video-intel, etc.). Recommended if it works.


Disable the use of damage information. This cause the whole screen to be redrawn every time, instead of the part of the screen has actually changed. Potentially degrades the performance, but might fix some artifacts.


Use X Sync fence to sync clients' draw calls, to make sure all draw calls are finished before picom starts drawing. Needed on nvidia-drivers with GLX backend for some users.

--glx-fshader-win SHADER

GLX backend: Use specified GLSL fragment shader for rendering window contents. See compton-default-fshader-win.glsl and compton-fake-transparency-fshader-win.glsl in the source tree for examples. Only works with --legacy-backends enabled.


Force all windows to be painted with blending. Useful if you have a --glx-fshader-win that could turn opaque pixels transparent.


Enable remote control via D-Bus. See the D-Bus API section below for more details.

--benchmark CYCLES

Benchmark mode. Repeatedly paint until reaching the specified cycles.

--benchmark-wid WINDOW_ID

Specify window ID to repaint in benchmark mode. If omitted or is 0, the whole screen is repainted.


Do not use EWMH to detect fullscreen windows. Reverts to checking if a window is fullscreen based only on its size and coordinates.


Dimming bright windows so their brightness doesn’t exceed this set value. Brightness of a window is estimated by averaging all pixels in the window, so this could comes with a performance hit. Setting this to 1.0 disables this behaviour. Requires --use-damage to be disabled. (default: 1.0)


Make transparent windows clip other windows like non-transparent windows do, instead of blending on top of them.

--transparent-clipping-exclude CONDITION

Specify a list of conditions of windows that should never have transparent clipping applied. Useful for screenshot tools, where you need to be able to see through transparent parts of the window.

--window-shader-fg SHADER

Specify GLSL fragment shader path for rendering window contents. Does not work when --legacy-backends is enabled. Shader is searched first relative to the directory the configuration file is in, then in the usual places for a configuration file. See section Shader Interface below for more details on the interface.

--window-shader-fg-rule SHADER:'CONDITION'

Specify GLSL fragment shader path for rendering window contents using patterns. Similar to --opacity-rule, arguments should be in the format of SHADER:CONDITION, e.g. "shader.frag:name = 'window'". Leading and trailing whitespaces in SHADER will be trimmed. If SHADER is "default", then the default shader will be used for the matching windows. (This also unfortunately means you can’t use a shader file named "default"). Does not work when --legacy-backends is enabled.

Use higher precision during rendering, and apply dither when presenting the rendered screen. Reduces banding artifacts, but might cause performance degradation. Only works with OpenGL.

Format of Conditions

Some options accept a condition string to match certain windows. A condition string is formed by one or more conditions, joined by logical operators.

A condition with "exists" operator looks like this:


With equals operator it looks like:


With greater-than/less-than operators it looks like:


NEGATION (optional) is one or more exclamation marks;

TARGET is either a predefined target name, or the name of a window property to match. Supported predefined targets are id, x, y, x2 (x + widthb), y2 (like x2), width, height, widthb (width + 2 * border_width), heightb (like widthb), border_width, fullscreen, override_redirect, argb (whether the window has an ARGB visual), focused, wmwin (whether the window looks like a WM window, i.e. has no child window with WM_STATE and is not override-redirected), bounding_shaped, rounded_corners (requires --detect-rounded-corners), client (ID of client window), window_type (window type in string), leader (ID of window leader), name, class_g (= WM_CLASS[1]), class_i (= WM_CLASS[0]), and role.

CLIENT/FRAME is a single @ if the window attribute should be be looked up on client window, nothing if on frame window;

INDEX (optional) is the index number of the property to look up. For example, [2] means look at the third value in the property. If not specified, the first value (index [0]) is used implicitly. Use the special value [*] to perform matching against all available property values using logical OR. Do not specify it for predefined targets.

FORMAT (optional) specifies the format of the property, 8, 16, or 32. On absence we use format X reports. Do not specify it for predefined or string targets.

TYPE is a single character representing the type of the property to match for: c for CARDINAL, a for ATOM, w for WINDOW, d for DRAWABLE, s for STRING (and any other string types, such as UTF8_STRING). Do not specify it for predefined targets.

OP QUALIFIER (optional), applicable only for equals operator, could be ? (ignore-case).

MATCH TYPE (optional), applicable only for equals operator, could be nothing (exact match), * (match anywhere), ^ (match from start), % (wildcard), or ~ (PCRE regular expression).

OPERATOR is one of = (equals), <, >, <=, =>, or nothing (exists). Exists operator checks whether a property exists on a window (but for predefined targets, exists means != 0 then).

PATTERN is either an integer or a string enclosed by single or double quotes. Python-3-style escape sequences are supported in the string format.

Supported logical operators are && (and) and || (or). && has higher precedence than ||, left-to-right associativity. Use parentheses to change precedence.


# If the window is focused
focused = 1
# If the window is not override-redirected
override_redirect = false
override_redirect != true
override_redirect != 1
# If the window is a menu
window_type *= "menu"
# If the window is marked hidden: _NET_WM_STATE contains _NET_WM_STATE_HIDDEN
# If the window is marked sticky: _NET_WM_STATE contains an atom that contains
# "sticky", ignore case
_NET_WM_STATE@[*]:a *?= "sticky"
# If the window name contains "Firefox", ignore case
name *?= "Firefox"
_NET_WM_NAME@:s *?= "Firefox"
# If the window name ends with "Firefox"
name %= "*Firefox"
name ~= "Firefox$"
# If the window has a property _COMPTON_SHADOW with value 0, type CARDINAL,
# format 32, value 0, on its frame window
# If the third value of _NET_FRAME_EXTENTS is less than 20, or there's no
# _NET_FRAME_EXTENTS property on client window
# The pattern here will be parsed as "dd4"
name = "\x64\x64\o64"

Legacy Format of Conditions

This is the old condition format we once used. Support of this format might be removed in the future.


TARGET is one of "n" (window name), "i" (window class instance), "g" (window general class), and "r" (window role).

TYPE is one of "e" (exact match), "a" (match anywhere), "s" (match from start), "w" (wildcard), and "p" (PCRE regular expressions, if compiled with the support).

FLAGS could be a series of flags. Currently the only defined flag is "i" (ignore case).

PATTERN is the actual pattern string.

Shader Interface

This secion describes the interface of a custom shader, how it is used by picom, and what parameters are passed by picom to the shader. This does not apply to the legacy backends.

A custom shader is a GLSL fragment shader program, which can be used to override the default way of how a window is rendered. If a custom shader is used, the default picom effects (e.g. dimming, color inversion, etc.) will no longer be automatically applied. It would be the custom shader’s responsibility to apply these effects.

The interface between picom and a custom shader is dependent on which backend is being used. The xrender backend doesn’t support shader at all. Here we descibe the interface provided by the glx backend.

The shader must define a function, vec4 window_shader(), which would be the entry point of the shader. The returned vec4 will be used to set gl_FragColor. A function, vec4 default_post_processing(vec4 c), is provided for applying the default picom effects to input color c.

The following uniform/input variables are made available to the shader:

in vec2 texcoord;             // texture coordinate of the fragment

uniform float opacity;        // opacity of the window (0.0 - 1.0)
uniform float dim;            // dimming factor of the window (0.0 - 1.0, higher means more dim)
uniform float corner_radius;  // corner radius of the window (pixels)
uniform float border_width;   // estimated border width of the window (pixels)
uniform bool invert_color;    // whether to invert the color of the window
uniform sampler2D tex;        // texture of the window
uniform vec2 effective_size;  // effective dimensions of the texture (repeats pixels if larger than tex)
uniform sampler2D brightness; // estimated brightness of the window, 1x1 texture
uniform float max_brightness; // configured maximum brightness of the window (0.0 - 1.0)
uniform float time;           // time in milliseconds, counting from an unspecified starting point

The default behavior of picom window rendering can be replicated by the following shader:

#version 330
in vec2 texcoord;             // texture coordinate of the fragment

uniform sampler2D tex;        // texture of the window

// Default window post-processing:
// 1) invert color
// 2) opacity / transparency
// 3) max-brightness clamping
// 4) rounded corners
vec4 default_post_processing(vec4 c);

// Default window shader:
// 1) fetch the specified pixel
// 2) apply default post-processing
vec4 window_shader() {
    vec2 texsize = textureSize(tex, 0);
    vec4 c = texture2D(tex, texcoord / texsize, 0);
    return default_post_processing(c);

The interface is expected to be mostly stable.

Configuration Files

picom could read from a configuration file if libconfig support is compiled in. If --config is not used, picom will seek for a configuration file in $XDG_CONFIG_HOME/picom.conf (~/.config/picom.conf, usually), then $XDG_CONFIG_HOME/picom/picom.conf, then $XDG_CONFIG_DIRS/picom.conf (often /etc/xdg/picom.conf), then $XDG_CONFIG_DIRS/picom/picom.conf.

picom uses general libconfig configuration file format. A sample configuration file is available as picom.sample.conf in the source tree. Most of commandline switches can be used as options in configuration file as well. For example, --vsync option documented above can be set in the configuration file using `vsync = `. Command line options will always overwrite the settings in the configuration file.

Window-type-specific settings are exposed only in configuration file and has the following format:

  WINDOW_TYPE = { fade = BOOL; shadow = BOOL; opacity = FLOAT; focus = BOOL; blur-background = BOOL; full-shadow = BOOL; clip-shadow-above = BOOL; redir-ignore = BOOL; };

WINDOW_TYPE is one of the 15 window types defined in EWMH standard: "unknown", "desktop", "dock", "toolbar", "menu", "utility", "splash", "dialog", "normal", "dropdown_menu", "popup_menu", "tooltip", "notification", "combo", and "dnd".

Following per window-type options are available:

fade, shadow

Controls window-type-specific shadow and fade settings.


Controls default opacity of the window type.


Controls whether the window of this type is to be always considered focused. (By default, all window types except "normal" and "dialog" has this on.)


Controls whether the window of this type will have its transparent background blurred.


Controls whether shadow is drawn under the parts of the window that you normally won’t be able to see. Useful when the window has parts of it transparent, and you want shadows in those areas.


Controls whether shadows that would have been drawn above the window should be clipped. Useful for dock windows that should have no shadow painted on top.


Controls whether this type of windows should cause screen to become redirected again after been unredirected. If you have --unredir-if-possible set, and doesn’t want certain window to cause unnecessary screen redirection, you can set this to true.


You can configure how the window background is blurred using a blur section in your configuration file. Here is an example:

  method = "gaussian";
  size = 10;
  deviation = 5.0;

Available options of the blur section are:


A string. Controls the blur method. Corresponds to the --blur-method command line option. Available choices are: none to disable blurring; gaussian for gaussian blur; box for box blur; kernel for convolution blur with a custom kernel; dual_kawase for dual-filter kawase blur. Note: gaussian, box and dual_kawase blur methods are not supported by the legacy backends. (default: none)


An integer. The size of the blur kernel, required by gaussian and box blur methods. For the kernel method, the size is included in the kernel. Corresponds to the --blur-size command line option (default: 3).


A floating point number. The standard deviation for the gaussian blur method. Corresponds to the --blur-deviation command line option (default: 0.84089642).


An integer in the range 0-20. The strength of the dual_kawase blur method. Corresponds to the --blur-strength command line option. If set to zero, the value requested by --blur-size is approximated (default: 5).


A string. The kernel to use for the kernel blur method, specified in the same format as the --blur-kern option. Corresponds to the --blur-kern command line option.



It’s possible to control picom via D-Bus messages, by running picom with --dbus and send messages to com.github.chjj.compton.<DISPLAY>. <DISPLAY> is the display used by picom, with all non-alphanumeric characters transformed to underscores. For DISPLAY=:0.0 you should use com.github.chjj.compton._0_0, for example.

The D-Bus methods and signals are not yet stable, thus undocumented right now.



Please submit bug reports to https://github.com/yshui/picom.

Out dated information in this man page is considered a bug.


Homepage: https://github.com/yshui/picom

See Also

xcompmgr(1), picom-trans(1)

Referenced By

configuration.nix(5), icewm(1), picom-trans(1).

02/13/2024 picom v11