Firefox's about: pages expose browser internals — configuration, debugging information, network state, and developer tools — that regular sites can't access. Here's a guide to the most useful ones for power users and developers.
Everyday About Pages
about:newtab
The new tab page. Can be customized with extensions or in settings.
about:home
Firefox's start page when no home page is set.
about:blank
An empty page with no content. Useful as a neutral starting state.
about:preferences (alias: about:settings)
Firefox Settings — same as the hamburger menu → Settings.
about:addons
Extension manager — install, enable/disable, configure extensions.
Diagnostic Pages
about:support
The most useful diagnostic page. Shows:
- Firefox version, build ID, and update channel
- OS, hardware, GPU information
- Crash reports
- Firefox profile location (helpful for backing up or copying profiles)
-
Modified preferences (any
about:configsetting you've changed from default) - Extension list with version numbers
- Security information (certificate store, etc.)
Copy "Raw Data" → paste to a support forum for bug reports.
about:crashes
All crash reports, with links to submit to Mozilla's crash reporting system. Each crash has a Report ID — useful for identifying intermittent crash bugs.
about:memory
Detailed memory breakdown:
- Memory usage by component (JavaScript heap, DOM nodes, network cache, etc.)
- Per-tab memory usage
- Extension memory
- "Minimize memory usage" button forces garbage collection
Useful for identifying memory leaks in pages or extensions.
about:performance
Real-time CPU and memory usage per tab and extension:
- Shows "sluggish" warnings for tabs using excessive resources
- Provides a rough timeline of activity
Configuration Pages
about:config
The advanced configuration editor. Search for any preference by name, change it:
Common useful settings:
browser.tabs.insertAfterCurrent = true
browser.urlbar.shortcuts.bookmarks = false
media.autoplay.default = 5 (block autoplay)
privacy.resistFingerprinting = true
full-screen-api.ignore-widgets = true
Warning: Many settings affect stability and security. Changes persist across sessions.
about:policies
Shows active enterprise policies (usually empty on personal machines). Enterprise Firefox deployments can enforce settings here.
Developer Pages
about:debugging
The most important page for extension developers:
- Load a temporary (unsigned) extension for testing
- Inspect extension background scripts and content scripts
- Debug extension processes with DevTools
- Connect to remote Firefox instances (Android, desktop)
Sub-pages:
-
about:debugging#/runtime/this-firefox— local Firefox -
about:debugging#/runtime/android— connected Android device
about:processes
Real-time view of all Firefox processes:
- Content processes per tab group
- Extension process
- GPU process
- Memory usage per process
- CPU time
about:telemetry
Everything Firefox is collecting and sending to Mozilla (if telemetry is enabled). Shows raw telemetry data — useful for privacy audits.
about:healthreport
Firefox Health Report — performance and stability metrics Firefox collects.
Network and Connectivity
about:networking
Network diagnostic information:
- DNS cache (resolved domains and their IPs)
- Socket pool (active connections)
- HTTP cache information
- WebSocket connections
- SPDY/HTTP2 connections
Useful for diagnosing DNS issues or understanding which connections are open.
about:neterror
Error page template for network errors. You normally see versions of this automatically (about:neterror?e=dnsNotFound etc.).
about:certificate
View the TLS certificate for a site. Navigate here after viewing a certificate in the HTTPS padlock popup.
Security Pages
about:logins
Firefox Lockwise — the built-in password manager. Shows all saved logins, lets you search, add, edit, and delete.
about:protections
Firefox privacy dashboard:
- How many trackers blocked this week
- Password health report
- Monitor (data breach notifications)
- VPN suggestions
Experimental Features
about:preferences#experimental (or about:preferences#labs)
Firefox Labs — experimental features you can opt into before they ship:
- Tab Groups (now shipped)
- Other in-development features
about:nightly (Firefox Nightly only)
Nightly-specific experiments and settings.
URL Format
about: pages use a special URL scheme:
about:support
about:config
about:debugging#/runtime/this-firefox
about:neterror?e=dnsNotFound&u=https%3A//example.com
They cannot be loaded in iframes (security restriction) and won't appear in browsing history (though about:config preferences persist).
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