WebKit Environment variables

This page documents some environment variables that you can use to change the behaviour of WebKit.

This documentation may be outdated or incomplete. If you wish, you can grep the sourcecode for getenv strings and update this document.

List of WebKit environment variables

• Use the following environment variables as:

  export Variable="Value"
  $WebKitCommand
  

Variable	Value	Meaning	WebKit ports
GIGACAGE_ENABLED	0	Disable gigacage (needed to use valgrind)	ALL
JavaScriptCoreUseJIT	0	Disable the JavaScript JIT	ALL
JSC_useFTLJIT	0	Disable the JavaScript FTL JIT	ALL
JSC_dumpOptions	3	Dumps all the JSC options available to tweak	ALL
JSC_${option from previous command}	${value}	${check with JSC_dumpOptions=3}	ALL
Malloc	1	Disable bmalloc memory allocator and use the system default one instead. On Darwin systems, also set __XPC_Malloc in order to pass on the value to child processes	ALL
MSE_MAX_BUFFER_SIZE	Examples: V:50M,audio:12k,TeXT:500K *:100M video:90M,T:100000	Set maximum SourceBuffer sizes for audio/video/text (when implemented) media types. Case insensitive, full type (audio, video, text) or compact type (a, v, t), wildcard (*) allowed, unit multipliers allowed (K, M).	WPE WebKit
WEBKIT_FORCE_COMPOSITING_MODE	1	Force Accelerated Compositing mode to be always on	WebKitGTK (since 2.10.5)
WEBKIT_DISABLE_COMPOSITING_MODE	1	Force Accelerated Compositing mode to be always off	WebKitGTK (since 2.10.9)
WEBKIT_INSPECTOR_SERVER	${ip.ad.dre.ss}:${port}	Enables the Remote WebInspector at http://${ip.ad.dre.ss}:${port} (NOTE: Use the same version of WebKit to load the address)	WebKitGTK
WEBKIT_SHOW_FPS	1	Shows a small square with the FPS measured at the top-right corner of the web view	WebKitGTK and WPE WebKit
WEBKIT_SAMPLE_MEMORY	1	Generates in /tmp some text files with memory stats.	WebKitGTK (since 2.15.2) and WPE WebKit
WEBKIT_FORCE_SANDBOX	1	Force enables the web process sandbox	WebKitGTK (since 2.23.1), not yet available for WPE WebKit
WEBKIT_ENABLE_DBUS_PROXY_LOGGING	1	Use for debugging the the sandbox's D-Bus proxy	WebKitGTK (since 2.23.1), not yet available for WPE WebKit
WEBKIT_WEBRTC_DISABLE_UNIFIED_PLAN	1	Use to disable Unified Plan as SDP format	WebKitGTK and WPE WebKit (since 2.23.1)
WEBKIT_FORCE_COMPLEX_TEXT	0	Confusing! Use only to disable complex text codepath	WebKitGTK (since 2.22.0), not available for WPE WebKit
WEBKIT_DISABLE_MEMORY_PRESSURE_MONITOR	1	Use to disable memory pressure monitor	WebKitGTK and WPE WebKit (since 2.22.0)
WEBKIT_GST_DISABLE_FAST_MALLOC	1	Use to disable the GStreamer FastMalloc allocator	WebKitGTK and WPE WebKit
WEBKIT_GST_MAX_AVC1_RESOLUTION		Set to 1080P, 720P or 480P to max out the H264/AVC1 resolution advertised as supported by the GStreamer media-capabilities backend	WebKitGTK and WPE WebKit (since 2.25.2)
WEBKIT_GST_USE_PLAYBIN3	1	Enable the next-generation playbin3 element for media playback (MSE not supported yet)	WebKitGTK and WPE WebKit
WEBKIT_GST_ENABLE_LEGACY_VAAPI	1 | Allow use of gstreamer-vaapi element for hardware decoding (deprecated)	WebKitGTK and WPE WebKit (since 2.36.3)
WEBKIT_EGL_PIXEL_LAYOUT	RGB565	Set the EGL pixel format used for rendering	WPE WebKit
WEBKIT_DEBUG	all or ${channel}	Enable debugging channels. Check WebKitGTK/Debugging#Loggingsupport for more info	WebKitGTK and WPE WebKit
WPE_SHELL_DISABLE_MEDIA_DISK_CACHE	1	Disable on-disk cache for regular (no MSE) video playback	WPE WebKit
WPE_SHELL_MEDIA_DISK_CACHE_PATH	/some/directory/path	Set custom path for on-disk cache for regular (no MSE) video playback	WPE WebKit