Note (October 2026): The chrome://…xul addresses in this 2012 list no longer open in current Firefox, because Mozilla removed XUL files from Firefox by the end of 2019. Working about: equivalents are listed below.
The funniest Firefox tricks today are its built-in Easter eggs: type about:robots or about:mozilla in the address bar. The old chrome://…xul shortcuts from 2012 stopped working after Mozilla removed XUL from Firefox (completed by the end of 2019); about:about now lists the hidden pages that still work.
Key Takeaways
- about:robots and about:mozilla are long-standing Firefox Easter eggs that still open by typing them in the address bar.
- The chrome://…xul tricks below were written for 2012-era Firefox; by the end of 2019 Mozilla had removed all XUL files from its main Firefox source repository.
- Firefox 57 (Firefox Quantum, November 2017) ended support for legacy XUL add-ons and moved to the WebExtensions API.
- about:about lists Firefox’s internal pages, such as about:preferences, about:addons, about:logins and about:processes.
- about:config changes advanced settings and carries a warning that edits can harm stability, security and performance.
New Tricks Of Firefox
Mozilla Firefox is one of the longest-running web browsers; version 1.0 was released on November 9, 2004. Firefox also hides some funny tricks. Firefox is known for its privacy and security features. Firefox is a free and open-source browser developed by the Mozilla Foundation and its subsidiary, the Mozilla Corporation, and it is available for Windows, macOS, Linux, Android and iOS. Below are some funny tricks of Firefox that were popular in 2012. These tricks showed parts of the Mozilla Firefox web browser that most users never see, and the modern equivalents still do.
Funny Tricks of Mozilla Firefox
In 2012-era Firefox, each of these addresses could be pasted into the address bar one by one. They no longer open in current Firefox, because Mozilla removed XUL files from Firefox by the end of 2019; the working about: equivalents are in the table further down.
chrome://global/content/alerts/alert.xul
In older versions, this opened Firefox’s small alert pop-up window, which could appear unexpectedly on the screen, so it looked like a dancing Firefox.
chrome://browser/content/preferences/sanitize.xul
In older versions, this opened the “Clear Private Data” window inside the current tab.
chrome://browser/content/aboutDialog.xul
In older versions, this opened the “About Firefox” dialog box inside the tab.
chrome://browser/content/credits.xhtml
In older versions, this opened a scrolling list of contributors’ names; in current Firefox, about:credits lists the people who contributed to Mozilla. The one’s who we must thank for creating Firefox
chrome://browser/content/browser.xul
In older versions, this loaded a second copy of the Firefox interface inside a tab, giving a Firefox-within-Firefox effect. Since Firefox 69 (September 2019), the main window file has been named browser.xhtml instead of browser.xul.
chrome://browser/content/preferences/preferences.xul
In older versions, this opened the Firefox options dialog box in a new tab; in current Firefox, settings open at about:preferences.
chrome://browser/content/bookmarks/bookmarksPanel.xul
In older versions, this opened the Firefox bookmarks panel in a new tab.
chrome://browser/content/history/history-panel.xul
In older versions, this opened your history in a new tab.
chrome://mozapps/content/extensions/extensions.xul?type=extensions
In older versions, this opened the extensions list in the current window; in current Firefox, about:addons does this.
chrome://browser/content/preferences/cookies.xul
In older versions, this opened the “cookies window” inside a tab in the Firefox window.
These addresses (the funny tricks of Mozilla Firefox) were shortcuts that opened Firefox features directly and helped make Firefox easier to use; in current versions, the about: pages below do the same job.
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Why the Old chrome:// Firefox Tricks Stopped Working
The chrome:// addresses above pointed to XUL files. XUL (XML User Interface Language) is the interface markup language devised at Netscape in 1997, and Firefox used it to draw its windows and dialogs.
Firefox 57, released in November 2017 and branded Firefox Quantum, ended support for legacy XUL add-ons and switched extensions to the WebExtensions API. By the end of 2019, Mozilla had removed all XUL files from its mozilla-central repository, and Firefox 69 (released September 3, 2019) renamed the main window file from browser.xul to browser.xhtml. As a result, the 2012 list above is now a piece of browser history rather than a working set of shortcuts.
Firefox Easter Eggs That Still Work
about:robots
about:robots is a Firefox-only Easter egg added in trunk builds from March 8, 2008. Its window title quotes “Klaatu barada nikto”, the famous line from the film The Day the Earth Stood Still, and its text refers to Isaac Asimov’s first law of robotics.
about:mozilla
about:mozilla shows a verse from The Book of Mozilla, a series of mock-scripture passages that date back to the Netscape browser. The about: scheme itself began in Netscape as an Easter egg that displayed information about the development team.
about:credits
about:credits lists people who contributed to Mozilla, which makes it the modern counterpart of the old scrolling credits trick above.
Useful Hidden about: Pages in Firefox
Firefox’s about: pages are internal addresses typed into the address bar. Typing about:about shows a list of them. The table maps common pages to what they do.
| about: page | What it shows | Replaces old trick |
|---|---|---|
| about:preferences | Firefox settings in a tab | preferences.xul |
| about:addons | Installed extensions, themes and plugins | extensions.xul |
| about:credits | List of Mozilla contributors | credits.xhtml |
| about:downloads | List of downloaded files | – |
| about:logins | Saved logins and passwords manager | – |
| about:processes | Memory and CPU use of running processes | – |
| about:support | Troubleshooting information | – |
| about:profiles | Profile management page | – |
| about:memory | Memory reports | – |
| about:crashes | Crash reports sent by the crash reporter | – |
| about:config | Advanced configuration settings | – |
about:preferences also accepts section anchors, such as about:preferences#privacy for privacy settings and about:preferences#search for search settings. For crash problems, see this guide on how to troubleshoot Firefox crashes.
How to Use about:config Safely
about:config is the Firefox page for viewing and changing configuration values that are not available in the normal settings screens. On first use, it shows a warning that changes can be harmful to the stability, security and performance of the browser.
- Type about:config in the address bar and press Enter.
- Read the warning and accept it only if you understand the risk.
- Search for the exact preference name you want to change.
- Note the original value before editing so you can reset it later.
- Restart Firefox if the change does not take effect immediately.
For safer everyday changes, the regular settings at about:preferences are the better route. Related reading: how to make your security settings better on Chrome and Mozilla.
Firefox at a Glance
- Firefox began in 2002 under the codename Phoenix and was renamed Mozilla Firefox on February 9, 2004.
- Firefox 1.0 was released on November 9, 2004, and reached 60 million downloads within nine months.
- Firefox usage share peaked at 32.21% in November 2009.
- As of July 2026, according to StatCounter, Firefox held a 6.3% share of desktop browser use, third behind Google Chrome (72%) and Microsoft Edge (10%), and ahead of Safari (5.2%).
For a comparison with other browsers, see the best browsers with low memory usage, and for testing sites across several browsers, read about cross-browser web testing.
Frequently Asked Questions
Do the chrome://…xul Firefox tricks still work?
No. The chrome://…xul tricks do not open in current Firefox, because Mozilla removed all XUL files from its main Firefox source repository by the end of 2019. The about: pages, such as about:preferences and about:addons, are the working replacements.
What is the Firefox robot Easter egg?
The Firefox robot Easter egg is about:robots. Typing it in the address bar opens a page whose title quotes “Klaatu barada nikto” from The Day the Earth Stood Still and whose text refers to Asimov’s first law of robotics.
How do I see all hidden pages in Firefox?
Type about:about in the Firefox address bar. It lists Firefox’s internal about: pages, which can be opened by clicking them.
Is it safe to change settings in about:config?
Changing about:config values can affect Firefox’s stability, security and performance, and Firefox warns about this on first use. Change only preferences you understand and note the original value first.
Why did Firefox stop supporting XUL?
Firefox moved to a multi-process architecture with Firefox 57 (Quantum) in November 2017. XUL add-ons often caused performance problems in that design, so Mozilla switched to the cross-browser WebExtensions API.
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