Quick guide to the most useful Firefox about: pages — the built-in diagnostic and configuration tools that most users never open.
about:config — Power User Settings
The full Firefox configuration panel. Type it in the address bar, click "Accept the Risk and Continue."
Most useful settings to know:
-
browser.tabs.unloadOnLowMemory→true: auto-suspend background tabs under memory pressure -
browser.tabs.loadBookmarksInTabs→true: open bookmarks in new tabs instead of current tab -
toolkit.legacyUserProfileCustomizations.stylesheets→true: enable CSS customization via userChrome.css
Search is the fastest way to find settings — the search bar filters in real time.
about:memory — Memory Debugging
Shows detailed memory usage for the entire Firefox process.
Key actions:
- "Measure" → generates current snapshot
- "Minimize memory usage" → frees cached memory without restart (often recovers 100-300MB)
- Filter by "extension" to see which add-ons are using the most memory
When Firefox feels slow, this is the first place to look.
about:performance — Real-Time Resource Monitor
Live CPU and memory usage per tab, per extension, and per background process.
Sort by memory to find which tabs are consuming the most. A single tab using 500MB+ is either a memory leak or a very heavy web app. Identifying and closing it can dramatically improve performance.
Useful for: finding the specific extension that's slowing things down, identifying memory-hungry tabs that should be closed or reloaded.
about:support — Troubleshooting Information
Complete diagnostic info about your Firefox installation: version, OS, graphics, crash reports, installed extensions, key settings.
Useful for: copying into bug reports, verifying your Firefox configuration, checking if hardware acceleration is working.
The "Refresh Firefox" button here resets Firefox to default settings without deleting bookmarks or passwords — useful when something's broken and you're not sure what.
about:telemetry — What Firefox Reports to Mozilla
If you're curious what telemetry Firefox sends, this shows it. You can disable telemetry in Settings → Privacy & Security → Firefox Data Collection.
about:addons — Extension Manager
You know this one. Quick tips:
- Each extension has a "Permissions" tab showing exactly what it can access
- The "Recommendations" tab shows extensions Mozilla actively recommends
- Right-clicking an extension in the toolbar → "Manage Extension" opens its options directly
about:networking — Network Diagnostics
Shows current DNS cache, open sockets, and HTTP connections. Useful for debugging connectivity issues or verifying that DNS-over-HTTPS is working.
about:crashes — Crash Reports
Lists Firefox crash reports with details. If Firefox has been crashing, this shows you when and why (to the extent Firefox can tell).
Most users will only ever need about:memory and about:performance from this list, but knowing they exist is half the battle. The next time Firefox feels slow, about:performance is faster than any external tool for diagnosing what's causing it.
Top comments (0)