Firefox and the "about" protocol

There is a lot of useful information about Firefox hidden away behind the about: URL protocol. The most useful is the URL about:config, which displays preferences and settings that can be inspected and changed.

Available about: URLs depend on your specific Firefox version. Here is a complete list of URLs in the about: pseudo protocol:

`about:` page	Description
`about:about`	Provides an overview of all about: pages available for your current Firefox version
`about:addons`	Add-ons Manager
`about:buildconfig`	Displays the configuration and platform used to build Firefox
`about:cache`	Displays information about the memory, disk, and appcache
`about:checkerboard`	Switches to the checkerboarding measurement page, which allows to detect checkerboarding issues
`about:config`	Provides a way to inspect and change Firefox preferences and settings
`about:compat`	Lists overriding site compatability fixes, linked to specific bug issues.
`about:crashes`	Lists all crashes, which happened during the runtime of Firefox (in case the user enabled the crash reporter)
`about:credits`	Lists all contributors to the Firefox project
`about:debugging`	Switches to the Developer Tools debugging page, which allows you to debug add-ons, tabs and Service Workers
`about:devtools`	Summarizes the developer tools and provides links to documentation for each tool
`about:downloads`	Displays all downloads done within Firefox
`about:home`	Start page of Firefox when opening a new window
`about:license`	Displays licensing information
`about:logo`	Firefox logo
`about:memory`	Provides a way to display memory usage, save it as report and run the GC and CC
`about:mozilla`	Special page showing a message from "The Book of Mozilla"
`about:networking`	Displays networking information
`about:newtab`	Start page when opening a new tab
`about:performance`	Displays memory and performance information about Firefox subprocesses/add-ons/tabs
`about:plugins`	Displays information about installed plugins
`about:policies`	Lists out the Firefox for Enterprise policies
`about:preferences`	Firefox settings (also available through Firefox menu > Options)
`about:privatebrowsing`	Start page when opening a private window
`about:profiles`	Display and manage Firefox profiles
`about:protections`	Privacy Protections report consisting of Enhanced Tracking Protection, Firefox Monitor and Firefox Lockwise data
`about:restartrequired`	A page users are sent to when Firefox requires a restart due to an update
`about:reader`	Indicates a web page has Firefox Reader View turned on. See Firefox Reader View for clutter-free web pages
`about:rights`	Displays rights information
`about:robots`	Special page showing notes about robots
`about:serviceworkers`	Displays currently running Service Workers
`about:studies`	Lists the Shield Studies that are installed
`about:sessionrestore`	Session restoration (displayed after a Firefox crash)
`about:support`	Troubleshooting information (also available through Firefox menu > ? (question mark) > Troubleshooting Information)
`about:sync-log`	Displays a synchronization protocol related to the Sync feature
`about:telemetry`	Displays telemetry data collected and sent to Mozilla while Firefox is running (in case the user enabled telemetry)
`about:url-classifier`	Displays the status of the URL Classifier services that Firefox uses (for example for Safe Browsing)
`about:webrtc`	Information about WebRTC usage
`about:welcome`	Page first displayed when Firefox is installed
`about:welcomeback`	Information page displayed after Firefox is reset

These URLs are defined in docshell/base/nsAboutRedirector.cpp within the kRedirMap array. The array maps most of the URLs, like config to URLs in the chrome: pseudo protocol, such as chrome://global/content/config.xul. The about location information is duplicated in docshell/build/nsDocShellModule.cpp.

Note: You must access about: protocol pages by typing them into the address bar. Attempts to navigate through window.location will throw — Error: Access to 'about:addons' from script denied.