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Mozilla Firefox
Mozilla Firefox Icon Mozilla Firefox wordmark
Firefox 21 on GNU/Linux
Developer(s) Mozilla Foundation
Mozilla Corporation Contributors
Initial release September 23, 2002 (2002-09-23)
Stable release 21.0 (May 14, 2013 (2013-05-14)) [±]
Preview release 22.0b1 (May 17, 2013 (2013-05-17)) [±]
Development status Active
Written in C/C++, JavaScript, CSS, XUL, XBL
Operating system Windows
Engine Gecko
Size 20 MB: Windows
37 MB: OS X
22-24 MB: Linux
19 MB: Android
94 MB: source code
Available in 89 locales (79 languages)
Type Web browser
Feed reader
License MPL
Standard(s) HTML5, CSS3, RSS, Atom

Mozilla Firefox is a free and open source web browser developed for Windows, OS X and Linux, with a mobile version for Android, by Mozilla Foundation and its subsidiary, the Mozilla Corporation. Firefox uses the Gecko layout engine to render web pages, which implements current and anticipated web standards.

As of October 2012, Firefox has approximately 20% to 24% of worldwide usage share of web browsers, making it the third most used web browser, according to different sources. According to Mozilla, Firefox counts over 450 million users around the world. The browser has had particular success in Indonesia, Germany and Poland, where it is the most popular browser with 65%, 47% and 47% of the market share, respectively.


The Firefox project began as an experimental branch of the Mozilla project by Dave Hyatt, Joe Hewitt and Blake Ross. They believed the commercial requirements of Netscape's sponsorship and developer-driven feature creep compromised the utility of the Mozilla browser. To combat what they saw as the Mozilla Suite's software bloat, they created a stand-alone browser, with which they intended to replace the Mozilla Suite. On April 3, 2003, the Mozilla Organization announced that they planned to change their focus from the Mozilla Suite to Firefox and Thunderbird.

Phoenix 0.1 screenshot

The Firefox project has undergone several name changes. Originally titled Phoenix, it was renamed because of trademark problems with Phoenix Technologies. The replacement name, Firebird, provoked an intense response from the Firebird free database software project. In response, the Mozilla Foundation stated that the browser should always bear the name Mozilla Firebird to avoid confusion with the database software. After further pressure from the database server's development community, on February 9, 2004, Mozilla Firebird became Mozilla Firefox, often referred to as simply Firefox. Mozilla prefers that Firefox be abbreviated as Fx or fx, though it is often abbreviated as FF. The Firefox project went through many versions before version 1.0 was released on November 9, 2004.

On October 4, 2012, Mozilla released a preview of the Metro interface version of Firefox, included in the Nightly 18 build, to be used in Windows 8. The nightly build was only available to those running the 64-bit RTM release of Windows 8.


Features include tabbed browsing, spell checking, incremental find, live bookmarking, smart bookmarks, a download manager, private browsing, location-aware browsing (also known as " geolocation") based on a Google service and an integrated search system that uses Google by default in most localizations. Functions can be added through extensions, created by third-party developers, of which there is a wide selection, a feature that has attracted many of Firefox's users.

Additionally, Firefox provides an environment for web developers in which they can use built-in tools, such as the Error Console or the DOM Inspector, or extensions, such as Firebug.


The result of the Acid3 test on Firefox 17.

Firefox implements many web standards, including HTML4 (partial HTML5), XML, XHTML, MathML, SVG 1.1 (partial), CSS (with extensions), ECMAScript ( JavaScript), DOM, XSLT, XPath, and APNG (Animated PNG) images with alpha transparency. Firefox also implements standards proposals created by the WHATWG such as client-side storage, and canvas element.

Firefox has passed the Acid2 standards-compliance test since version 3.0. Mozilla had originally stated that they did not intend for Firefox to pass the Acid3 test fully because they believed that the SVG fonts part of the test had become outdated and irrelevant, due to WOFF being agreed upon as a standard by all major browser makers. Because the SVG font tests were removed from the Acid3 test in September 2011, Firefox 4 and greater scored 100/100.

Firefox also implements a proprietary protocol from Google called "Safe Browsing", used to exchange data related with phishing and malware protection.


Firefox uses a sandbox security model, and limits scripts from accessing data from other web sites based on the same origin policy. It uses SSL/TLS to protect communications with web servers using strong cryptography when using the HTTPS protocol. It also provides support for web applications to use smartcards for authentication purposes.

The Mozilla Foundation offers a "bug bounty" (up to 3000 USD cash reward and a Mozilla T-shirt) to researchers who discover severe security holes in Firefox. Official guidelines for handling security vulnerabilities discourage early disclosure of vulnerabilities so as not to give potential attackers an advantage in creating exploits.

Because Firefox generally has fewer publicly known unpatched security vulnerabilities than Internet Explorer (see Comparison of web browsers), improved security is often cited as a reason to switch from Internet Explorer to Firefox. The Washington Post reports that exploit code for known critical unpatched security vulnerabilities in Internet Explorer was available for 284 days in 2006. In comparison, exploit code for known, critical security vulnerabilities in Firefox was available for 9 days before Mozilla issued a patch to remedy the problem.

A 2006 Symantec study showed that, although Firefox had surpassed other browsers in the number of vendor-confirmed vulnerabilities that year through September, these vulnerabilities were patched far more quickly than those found in other browsers – Firefox's vulnerabilities were fixed on average one day after the exploit code was made available, as compared to nine days for Internet Explorer. Symantec later clarified their statement, saying that Firefox still had fewer security vulnerabilities than Internet Explorer, as counted by security researchers.

In 2010 a study of the National Institute of Standards and Technology (NIST) based on data compiled from the National Vulnerability Database (NVD) Firefox was listed as the 5th most vulnerable desktop software, Internet Explorer ranked 8th, and Google Chrome as 1st.

InfoWorld has cited security experts saying that as Firefox becomes more popular, more vulnerabilities will be found, a claim that Mitchell Baker, president of the Mozilla Foundation, has denied: "There is this idea that market share alone will make you have more vulnerabilities. It is not relational at all."

In October 2009, Microsoft's security engineers acknowledged that Firefox was vulnerable since February of that year due to a .NET Framework 3.5 SP1 Windows update that silently installed a buggy 'Windows Presentation Foundation' plug-in into Firefox. This vulnerability has since been patched by Microsoft.

As of February 11, 2011, Firefox 3.6 had no known unpatched security vulnerabilities according to Secunia. Internet Explorer 8 had five unpatched security vulnerabilities, the worst being rated "Less Critical" by Secunia.

Mozilla claims that all patched vulnerabilities of Mozilla products are publicly listed.

On January 28, 2013, Mozilla was recognized as the most trusted internet company for privacy in 2012. This study was performed by Ponemon Institute and was a result of a survey from more than 100,000 consumers in the United States.

As of February 22, 2013, it was announced that Firefox release candidate 22 would be blocking all third-party cookies. This new policy ensures that only visited websites may use cookies to track you across the web. The Firefox team plans on implementing such features to other technologies such as HTML5 Web Storage.


When Firefox is upgraded to version 7.0, an information bar will appear asking users whether they would like to send performance statistics (also known as “telemetry”) to Mozilla. According to Mozilla's privacy policy, these statistics are stored only in aggregate format, and the only personally identifiable information transmitted is the user's IP address.


Firefox is a heavily localized web browser. The first official release in November 2004 was available in 24 different languages and for 28 locales, including British English/American English, European Spanish/ Argentine Spanish and Chinese in Traditional Chinese characters/ Simplified Chinese characters. Currently supported versions 17.0.6esr and 21.0 are available in 89 locales (79 languages).

Platform availability

Firefox for desktop is available for Windows, OS X and Linux. Firefox for mobile is available for Android.


Firefox source code is free software, with most of it being released under the Mozilla Public License (MPL). This license permits anyone to view, modify, and/or redistribute the source code, and several publicly released applications have been built on it; for example, Netscape, Flock, Miro, Iceweasel, and Songbird make use of code from Firefox.

In the past, Firefox was licensed solely under the MPL, which the Free Software Foundation criticized for being weak copyleft; the license permitted, in limited ways, proprietary derivative works. Additionally, code only licensed under the MPL could not legally be linked with code under the GPL. To address these concerns, Mozilla re-licensed most of Firefox under the tri-license scheme of MPL, GPL, or LGPL. Since the re-licensing, developers were free to choose the license under which they received most of the code, to suit their intended use: GPL or LGPL linking and derivative works when one of those licenses is chosen, or MPL use (including the possibility of proprietary derivative works) if they chose the MPL. However, on January 3, 2012, Mozilla released the GPL-compatible MPL 2.0, and with the release of Firefox 13 on June 5, 2012, Mozilla used it to replace the tri-licensing scheme.

The crash reporting service was initially closed source, but switched with version 3 from a program called Talkback to the open source Breakpad & Socorro.

The name "Mozilla Firefox" is a registered trademark; along with the official Firefox logo, it may only be used under certain terms and conditions. Anyone may redistribute the official binaries in unmodified form and use the Firefox name and branding for such distribution, but restrictions are placed on distributions which modify the underlying source code. The name "Firefox" derives from a nickname of the red panda.

Mozilla has placed the Firefox logo files under open-source licenses, but its trademark guidelines do not allow displaying altered or similar logos in contexts where trademark law applies.

Logo used for Iceweasel

There has been some controversy over the Mozilla Foundation's intentions in stopping certain open source distributions from using the "Firefox" trademark. Mozilla Foundation Chairperson Mitchell Baker explained in an interview in 2007 that distributions could freely use the Firefox trademark if they did not modify source-code, and that the Mozilla Foundation's only concern was with users getting a consistent experience when they used "Firefox".

To allow distributions of the code without using the official branding, the Firefox source code contains a "branding switch". This switch allows the code to be compiled without the official logo and name, for example to produce a derivative work unencumbered by restrictions on the Firefox trademark (this is also often used for alphas of future Firefox versions). In the unbranded compilation the trademarked logo and name are replaced with a freely distributable generic globe logo and the name of the release series from which the modified version was derived.

Distributing modified versions of Firefox under the "Firefox" name requires explicit approval from Mozilla for the changes made to the underlying code, and requires the use of all of the official branding. For example, it is not permissible to use the name "Firefox" without also using the official logo. When the Debian project decided to stop using the official Firefox logo in 2006 (because Mozilla's copyright restrictions at the time were incompatible with Debian's guidelines), they were told by a representative of the Mozilla Foundation that this was not acceptable, and were asked either to comply with the published trademark guidelines or cease using the "Firefox" name in their distribution. Ultimately, Debian switched to branding their modified version of Firefox " Iceweasel", along with other Mozilla software.

Branding and visual identity

Early Firebird and Phoenix releases of Firefox were considered to have had reasonable visual designs, but were not up to the same standards as many professionally released software packages. In October 2003, professional interface designer Steven Garrity wrote an article covering everything he considered to be wrong with Mozilla's visual identity. The page received a great deal of attention; the majority of criticism leveled at the article fell along the lines of "where's the patch?"

Blue globe artwork is distributed with Firefox source code, and is explicitly not protected as a trademark

Shortly afterwards, Garrity was invited by the Mozilla Foundation to head up the new visual identity team. The release of Firefox 0.8 in February 2004 saw the introduction of the new branding efforts, including new icon designs by silverorange, a group of web developers with a long-standing relationship with Mozilla, with final renderings by Jon Hicks, who had previously worked on Camino. The logo was later revised and updated, fixing several flaws found when it was enlarged.

The animal shown in the logo is a stylized fox, although "firefox" is considered to be a common name for the red panda. The panda, according to Hicks, "didn't really conjure up the right imagery" and wasn't widely known. The logo was chosen to make an impression while not shouting out with overdone artwork. It had to stand out in the user's mind, be easy for others to remember, and stand out without causing too much distraction when seen among other icons.

The Firefox icon is a trademark used to designate the official Mozilla build of the Firefox software and builds of official distribution partners. For this reason, Debian and other software distributors who distribute patched or modified versions of Firefox do not use the icon.

Logo history :

Other logos are also used for specific versions of the software:


The rapid adoption of Firefox, 100 million downloads in its first year of availability, followed a series of aggressive marketing campaigns starting in 2004 with a series of events Blake Ross and Asa Dotzler called "marketing weeks".

On September 12, 2004, a marketing portal dubbed "Spread Firefox" (SFX) debuted along with the Firefox Preview Release, creating a centralized space for the discussion of various marketing techniques. A two-page ad in the December 16 edition of the New York Times, placed by Mozilla Foundation in coordination with Spread Firefox, featured the names of the thousands of people worldwide who contributed to the Mozilla Foundation's fundraising campaign to support the launch of the Firefox 1.0 web browser. SFX portal enhanced the "Get Firefox" button program, giving users "referrer points" as an incentive. The site lists the top 250 referrers. From time to time, the SFX team or SFX members launch marketing events organized at the Spread Firefox website. As a part of the Spread Firefox campaign, there was an attempt to break the world download record with the release of Firefox 3. This resulted in an official certified Guinness world record, with over eight million downloads.

The "World Firefox Day" campaign started on July 15, 2006, the third anniversary of the founding of the Mozilla Foundation, and ran until September 15, 2006. Participants registered themselves and a friend on the website for nomination to have their names displayed on the Firefox Friends Wall, a digital wall that will be displayed at the headquarters of the Mozilla Foundation.

In December 2007, Mozilla launched Live Chat, a service allowing users to seek technical support from volunteers. Because Live chat is kept running by volunteers, it is only available when they are online.

On February 21, 2008 in honour of reaching 500 million downloads, the Firefox community celebrated by visiting FreeRice to earn 500 million grains of rice.

Some of Firefox's contributors made a crop circle of the Firefox logo in an oat field near Amity, Oregon, near the intersection of Lafayette Highway and Walnut Hill Road.

In February 2011, Mozilla announced that it would be retiring Spread Firefox (SFX). Three months later, in May 2011, Mozilla officially closed Spread Firefox. Mozilla wrote that "there are currently plans to create a new iteration of this website [Spread Firefox] at a later date."


Most used web browser by country as of April 2013 according to StatCounter.
Market Share Overview
According to StatCounter data

April 2013

Browser  % of Fx  % of Total
Firefox 1 0.05% 0.01%
Firefox 1.5 0.05% 0.01%
Firefox 2 0.15% 0.03%
Firefox 3 0.55% 0.11%
Firefox 3.5 0.35% 0.07%
Firefox 3.6 2.19% 0.44%
Firefox 4 0.70% 0.14%
Firefox 5 0.45% 0.09%
Firefox 6 0.40% 0.08%
Firefox 7 0.40% 0.08%
Firefox 8 0.60% 0.12%
Firefox 9 0.60% 0.12%
Firefox 10
Firefox 10 ESR
1.15% 0.23%
Firefox 11 1.00% 0.20%
Firefox 12 2.34% 0.47%
Firefox 13 1.20% 0.24%
Firefox 14 1.55% 0.31%
Firefox 15 2.29% 0.46%
Firefox 16 4.09% 0.82%
Firefox 17
Firefox 17 ESR
1.74% 0.35%
Firefox 18 1.99% 0.40%
Firefox 19 27.02% 5.42%
Firefox 20 47.21% 9.47%
Firefox 21 1.79% 0.36%
Firefox 22 0.10% 0.02%
Firefox 23 0.10% 0.02%
All variants 100% 20.06%


  • calls Firefox "the best browser" in a commentary piece.
  • PC World names Firefox "Product of the Year" in 2005 on their "100 Best Products of 2005" list.
  • PC Pro Real World Award (Mozilla Foundation), December 2005
  • CNET Editors' Choice, November 2005
  • UK Usability Professionals' Association Best Software Award, November 2005
  • Macworld Editor's Choice with a 4.5 Mice Rating, November 2005
  • Softpedia User’s Choice Award, September 2005
  • TUX 2005 Readers' Choice Award, September 2005
  • Forbes Favorite of Best of the Web picks, April 2005
  • PC Magazine Editor’s Choice Award, May 2005
  • After the release of Firefox 2 and Internet Explorer 7, PC World reviewed both and declared that Firefox was the better browser.
  • PC Magazine Editors' Choice, October 2006
  • CNET Editors' Choice, October 2006
  • PC World's 100 Best Products of 2006, July 2006
  • PC Magazine Software and Development Tools Award, January 2006
  • Which? Magazine names Firefox its "Best Buy" web browser.
  • Webware 100 winner, June 2007
  • PC World 100 Best Products of 2007, May 2007
  • CNET compares Safari, Chrome, Firefox, and Internet Explorer in their "Battle of the Browsers" in terms of performance, security, and features, where Firefox is selected as a favorite.
  • PC Magazine Editors' Choice, June 2008
  • PC World 100 Best Products of 2008, May 2008
  • Webware 100 winner, April 2008
  • Webware 100 winner, May 2009
  • Members Choice Awards, February 2009
  • CNET Top 10 Mac Downloads, December 2010
  • Tom's Hardware WBGP 7, September 2011
  • CNET Editors' Choice, March 2011
  • In February, Tom's Hardware compared Safari 5.1.2, Google Chrome 17, Mozilla Firefox 10, Opera 11.61 and Microsoft Internet Explorer 9 on both Ubuntu 11.10 and Windows 7 (Internet Explorer and Safari excluded from Ubuntu because of OS availability) in a "Web Browser Grand Prix". They concluded, that based on performance, Chrome 17 was selected as their favorite on Ubuntu – but they also concluded that on Windows, Firefox 10 was their favorite.


In December 2005, Internet Week ran an article in which many readers reported high memory usage in Firefox 1.5. Mozilla developers said that the higher memory use of Firefox 1.5 was at least partially due to the new fast backwards-and-forwards (FastBack) feature. Other known causes of memory problems were malfunctioning extensions such as Google Toolbar and some older versions of Adblock, or plug-ins, such as older versions of Adobe Acrobat Reader. When PC Magazine compared memory usage of Firefox 2, Opera 9, and Internet Explorer 7, they found that Firefox used approximately as much memory as the other two browsers.

Softpedia noted that Firefox 1.5 took longer to start up than other browsers, which was confirmed by further speed tests. IE 6 launched more swiftly than Firefox 1.5 on Windows XP since many of its components were built into the OS and loaded during system startup. As a workaround for the issue, a preloader application was created that loaded components of Firefox on startup, similar to Internet Explorer. A Windows Vista feature called SuperFetch performs a similar task of preloading Firefox if it is used often enough.

Tests performed by PC World and Zimbra in 2006 indicated that Firefox 2 used less memory than Internet Explorer 7. Firefox 3 used less memory than Internet Explorer 7, Opera 9.50 Beta, Safari 3.1 Beta, and Firefox 2 in tests performed by Mozilla, CyberNet, and The Browser World. In mid 2009, Betanews benchmarked Firefox 3.5 and declared that it performed "nearly ten times better on XP than Microsoft Internet Explorer 7".

In January 2010, Lifehacker compared the performance of Firefox 3.5, Firefox 3.6, Google Chrome 4 (stable and Dev versions), Safari 4, and Opera (10.1 stable and 10.5 pre-alpha versions). Lifehacker timed how long browsers took to start and reach a page (both right after boot-up and after running at least once already), timed how long browsers took to load nine tabs at once, tested JavaScript speeds using Mozilla's Dromaeo online suite (which implements Apple's SunSpider and Google's V8 tests) and measured memory usage using Windows 7's process manager. They concluded that Firefox 3.5 and 3.6 were the fifth and sixth fastest browsers respectively on startup, 3.5 was third and 3.6 was sixth fastest to load nine tabs at once, 3.5 was sixth and 3.6 was fifth fastest on the JavaScript tests. They also concluded that Firefox 3.6 was the most efficient with memory usage followed by Firefox 3.5.

In February 2012, Tom's Hardware performance tested Chrome 17, Firefox 10, Internet Explorer 9, Opera 11.61, and Safari 5.1.2 on Windows 7. Tom's Hardware summarized their tests into four categories: Performance, Efficiency, Reliability, and Conformance. In the performance category they tested HTML 5, Java, JavaScript, DOM, CSS 3, Flash, Silverlight, and WebGL – they also tested start up time and page load time. The performance tests showed that Firefox was either "acceptable" or "strong" in most categories, winning three categories (HTML5, HTML5 Hardware acceleration, and Java) only finishing "weak" in CSS performance. In the efficiency tests, Tom's Hardware tested memory usage and management. In this category, it determined that Firefox was only "acceptable" at performing light memory usage, while it was "strong" at performing heavy memory usage. In the reliability category, Firefox performed a "strong" amount of proper page loads. In the final category, conformance, it was determined that Firefox had "strong" conformance for JavaScript and HTML5. In conclusion, Tom's Hardware determined that Firefox was the best browser for Windows 7 OS, but that it only narrowly beat out Google Chrome.

Market adoption

Usage share of web browsers according to StatCounter.
Usage share of web browsers (November 2012 – StatCounter)

Downloads have continued at an increasing rate since Firefox 1.0 was released in November 2004, and as of July 31, 2009 Firefox has been downloaded over one billion times. This number does not include downloads using software updates or those from third-party websites. They do not represent a user count, as one download may be installed on many machines, one person may download the software multiple times, or the software may be obtained from a third party. According to Mozilla, Firefox has more than 450 million users as of October 2012.

In July 2010, all IBM employees (about 400,000) were asked to use Firefox as their default browser.

Firefox was the second-most used web browser until December 2011, when Google Chrome surpassed it.

As of May 2012, Firefox was the third most widely used browser, with approximately 25% of worldwide usage share of web browsers. According to StatCounter, Firefox usage peaked in November 2009 and usage share remained stagnant until October 2010 when it lost market share, a trend that continued for over a year. Its first consistent gains in usage share since September 2010 occurred in February through May 2012 before declining again in June and July.

Release history

Colour Meaning
Red Former release; no longer supported
Yellow Former release; still supported
Green Current supported release
Blue Future release
Release history
Version Release date Gecko
Release notes
0.1 2002-09-23 1.2
  • First release
0.2 2002-10-01
  • Web form auto-complete
  • Sidebar is back
    • Downloads Sidebar
    • Bookmarks Sidebar
    • History Sidebar
  • Extension management
  • Toolbar customization
  • Search bar
  • Improved preference defaults
  • Speed improvements
  • Ctrl+Mousewheel to resize fonts
  • Bug fixes
0.3 2002-10-14
  • Image Blocking
  • Pop-up Blocking Whitelist
  • Bookmarks Changes
  • Global Go Menu and Other Menu Changes
  • Tabbed Browsing Improvements
  • Size and Speed Improvements
  • Bug fixes
0.4 2002-10-19 1.3
  • Improvements to pop-up blocking
  • Improvements to toolbar customization
  • Improvements to tabbed browsing and shortcut keys
  • Type ahead find returns
  • Address bar gets smarter
  • Themes
  • Bug fixes
0.5 2002-12-07
  • Multiple homepages
  • Intellimouse 5-button support
  • Sidebar remembers its state across sessions
  • Download fixes
  • History improvements
  • Accessibility improvements
  • Size and memory reduction
  • Performance improvements
  • Stability improvements
  • Better Windows appearance
  • Many more new themes
  • Many bug fixes
0.6 2003-05-17 1.5
  • New default theme
  • Redesigned Preferences window
  • Improved Privacy Options
  • Improved Bookmarks
  • Talkback enabled to tell Mozilla why the browser crashed
  • Automatic Image Resizing
  • Smooth Scrolling
  • Access to more preferences through about:config
  • Custom profile save location
  • Mac OS X compatibility
  • Lots of bug fixes
0.7 2003-10-15
  • Advanced preferences panel
  • Download/helper apps preferences panel
  • Cookie whitelisting
  • New password manager (all passwords now stored encrypted)
  • Web panels (like Mozilla's sidebar panels)
  • Alternate stylesheet support (through a status bar button)
  • Send Page, Send Link, and Send Image menu items
  • Autoscroll
  • Lots of bug fixes and other small improvements
0.8 2004-02-09 1.6
  • Windows Installer
  • Download Manager
  • New Add Bookmark Dialog
  • Work Offline
  • Better Handling of File Types
  • New XPInstall Frontend
  • New default theme for Mac OS X
  • Lots of bug fixes and improvements
0.9 2004-05-15 1.7
  • New Default Theme
  • Comprehensive Data Migration from Internet Explorer
  • Extension/Theme Manager
  • Smaller Download
  • Online help system
  • Lots of bug fixes and improvements
1.0 2004-11-09
  • Better Tabbed Browsing Controls
  • Horde of bug fixes
1.0.8 2006-04-13
  • Security fixes
  • Bug fixes
  • Stability fixes
1.5 2005-11-29 1.8
  • Dropped support for Mac OS X v10.1, minimum is now Mac OS X v10.2
  • Private data clear data
  • Back and forward now fast
  • Improved web standards
    • Improved HTML
    • Improved CSS
    • Improved HTTP
    • Improved JavaScript/ DOM
    • SVG compatibility
  • Huge amount of bug fixes 2007-05-30
  • Bug fixes
  • Stability fixes
  • Security fixes
2.0 2006-10-24 1.8.1
  • Visual Refresh of main theme
  • Built-in phishing protection
  • Enhanced search capabilities
  • Improved tabbed browsing
  • Resuming your browsing session (session restore)
  • Previewing and subscribing to Web feeds
  • Inline spell checking
  • Live Web Titles
  • Improved Add-ons manager
  • JavaScript 1.7
  • Extended search plugin format (predictive search)
  • Improved security with extension system
  • Client-side session and persistent storage
  • SVG text support
  • New Windows installer 2008-12-18
  • Bug fixes
  • Security fixes
  • Stability fixes
3.0 2008-06-17 1.9
  • One-click site info
  • Malware Protection
  • New Web Forgery Protection page
  • New SSL error pages
  • Add-ons and Plugin version check
  • Secure add-on updates
  • Anti-virus integration with download manager
  • Vista Parental Controls
  • Effective top-level domain (eTLD) service better restricts cookies and other restricted content to a single domain.
  • Better protection against cross-site JSON data leaks.
  • Easier password management – save passwords after successful login
  • Simplified add-on installation from 3rd party’s
  • New Download Manager
  • Resumable downloading after closing the browser
  • Full page zoom
  • Podcasts and Videocasts can be associated with your media playback tools
  • Tab scrolling and quickmenu
  • Save what you were doing - Firefox 3 will prompt users to save tabs on exit.
  • Optimized Open in Tabs behaviour
  • Location and Search bar size can now be customized with a simple resizer item.
  • Text selection improvements (select multiple selections of text)
  • Find toolbar: the Find toolbar now opens with the current selection.
  • Plugin management with the add-on manager
  • Improved integration with Windows
  • Improved integration with the Mac
  • Integration with Linux GTK theme
  • Bookmark star button
  • Bookmark tags
  • Smart Location Bar
  • Library of bookmarks, history, etc.
  • Smart Bookmark Folders
  • Web-based protocol handlers for mail:to
  • Download & Install Add-ons from the Add-on manager
  • Easy to use Download Actions
  • New graphics and font handling in Gecko 1.9 provide rendering improvements in:
  • CSS
  • SVG
  • Display of fonts with ligatures and complex scripts
  • Colour management of images with capabilities
  • Offline support for web applications
  • Improved speed
  • Reduced memory usage
  • Increased reliability
  • 25000 total code changes
  • Security fixes
  • Stability fixes
3.0.19 2010-03-30
  • Fixed several security problems.
  • Fixed several stability issues.
3.5 2009-06-30 1.9.1
  • Support for the HTML5
  • Improved tools for controlling your private data, including a Private Browsing Mode
  • Better web application performance using the new TraceMonkey JavaScript engine
  • The ability to share your location with websites using Location Aware Browsing
  • Support for native JSON, and web worker threads
  • Improvements to the Gecko layout engine, including speculative parsing for faster content rendering
  • Support for new web technologies such as:
    • Downloadable fonts
    • CSS media queries
    • New transformations and properties
    • JavaScript query selectors
    • HTML5 local storage and offline application storage
    • text
    • ICC profiles
    • SVG transforms.
3.5.19 2011-04-28
  • Fixed several security issues
  • Fixed several stability issues
3.6 2010-01-21 1.9.2
  • Support for Persona themes
  • Protection from out-of-date plugins to keep users safer as they browse.
  • Open, native video can now be displayed full screen and supports poster frames.
  • Improved JavaScript performance, overall browser responsiveness, and startup time.
  • The ability for web developers to indicate that scripts should run asynchronously to speed up page load times.
  • Continued support for downloadable web fonts using the new WOFF font format.
  • Support for new CSS attributes such as gradients, background sizing, and pointer events.
  • Support for new DOM and HTML5 specifications including the Drag & Drop API and the File API, which allow for more interactive web pages.
  • Changes to how third-party software can integrate with Firefox in order to prevent crashes.
3.6.28 2012-03-13
  • Added Out-of-process plugins
  • Fixed several security issues
  • Fixed several stability issues
4.0 2011-03-22 2.0
  • Firefox 4 is available in over 80 languages
  • Uses JägerMonkey, a faster JavaScript engine
  • Support for Do Not Track ("DNT") header that allows users to opt-out of behavioural advertising
  • Firefox Sync is included by default
  • Graphic rendering is now hardware-accelerated using Direct3D 9 (Windows XP), Direct3D 10 (Windows Vista & 7), and OpenGL on Mac OS
  • Direct2D Hardware Acceleration is now on by default for Windows 7 users
  • WebGL is enabled on all platforms that have a capable graphics card with updated drivers
  • Native support for the HD HTML5 WebM video format, hardware accelerated where available
  • Firefox button has a new look for Windows Vista and Windows 7 users
  • Tabs are now on top by default on Windows, Mac OS X, and Linux
  • You can search for and switch to already open tabs in the Smart Location Bar
  • The stop and reload buttons have been merged into a single button on Windows, Mac OS X, and Linux
  • The Bookmarks Toolbar has been replaced with a Bookmarks Button by default (you can switch it back if you'd like)
  • Crash protection when there is a crash in Adobe Flash Player, Apple QuickTime or Microsoft Silverlight plugins
  • You can turn any tab into an "App Tab"
  • The default homepage design has been refreshed
  • Overhaul of the bookmarks and history code, enabling faster bookmarking and startup performance
  • Per-compartment garbage collection is now enabled, reducing work done during complex animations
  • Additional polish for the Firefox add-on Manager
  • Improved web typography using OpenType with support for ligatures, kerning and font variants
  • Web developers can animate content using CSS Transitions
  • Responsiveness and scrolling improvements from the new retained layers layout system
  • HTML5 Forms API makes web based forms easier to implement and validate
  • Support for the new proposed Audio Data API
  • Support for HSTS security protocol allowing sites to insist that they only be loaded over SSL
  • A new feature called Panorama gives users a visual overview of all open tabs, allowing them to be sorted and grouped
  • An experimental API is included to provide more efficient Javascript animations
  • Firefox now supports the HTML5 video "buffered" property
  • Changes to how XPCOM components are registered in order to help startup time and process separation
  • New Addons Manager and extension management API
  • Significant API improvements are available for JS-ctypes, a foreign function interface for extensions
  • CSS Transitions are partially supported
  • Core Animation rendering model for plugins on Mac OS X
  • Web developers can update the URL field without reloading the page using HTML History APIs
  • More responsive page rendering using lazy frame construction
  • Link history lookup is done asynchronously to provide better responsiveness during pageload
  • CSS :visited selectors have been changed to block websites from being able to check a user's browsing history
  • New HTML5 parser
  • Support for more HTML5 form controls
  • Web authors can now get touch events from Firefox users on Windows 7 machines
  • A new way of representing values in JavaScript that allows Firefox to execute heavy, numeric code more efficiently
4.0.1 2011-04-28
  • Fixed several security issues
  • Fixed several stability issues
5.0 2011-06-21 5.0
  • Better standards support for HTML5, CSS3, MathML, XHR and SMIL
  • Better visibility for the Do not track header preference
  • Stability and security improvements
  • Better tuned HTTP idle connection logic
  • Improved canvas, JavaScript, memory, and networking performance
  • Improved spell checking for some locales
  • Improved desktop environment integration for Linux users
  • Better WebGL security (WebGL content can no longer load cross-domain textures).
  • Background tabs have setTimeout and setInterval clamped to 1000 ms to improve performance
5.0.1 2011-07-11
  • Fixed an issue in Mac OS X 10.7 that could cause Firefox to crash
  • Fixed an issue caused by Apple's "Java for Mac OS X 10.6 Update 5" where the Java plugin would not be loaded
6.0 2011-08-16 6.0
  • about:permissions, a permissions manager. The user can choose what information can be shared with sites, e.g. location.
  • The address bar now highlights the domain of the website you are visiting.
  • Streamlined the look of the site identity block
  • Added support for the latest draft version of WebSockets with a prefixed API
  • Added support for EventSource / server-sent events
  • Added support for window.matchMedia
  • Added Scratchpad, an interactive JavaScript prototyping environment
  • Added a new Web Developer menu item and moved development-related items into it
  • Improved usability of the Web Console
  • Improved the discoverability of Firefox Sync
  • Reduced browser startup time when using Panorama
  • Fixed several stability issues
  • Fixed several security issues
6.0.2 2011-09-06
  • Revoked the root certificate for DigiNotar due to fraudulent SSL certificate issuance
  • Removed trust exceptions for certificates issued by Staat der Nederlanden
  • Resolved an issue with websites
7.0 2011-09-27 7.0
  • Drastically improved memory handling for certain use cases
  • Added a new rendering backend to speed up Canvas operations on Windows systems
  • Bookmark and password changes now sync almost instantly when using Firefox Sync
  • The 'http://' URL prefix is now hidden by default.
  • Added support for text-overflow: ellipsis
  • Added support for the Web Timing specification
  • Enhanced support for MathML
  • The WebSocket protocol has been updated from version 7 to version 8.
  • Added an opt-in system for users to send performance data back to Mozilla to improve future versions of Firefox
  • Fixed several stability issues
  • Fixed several security issues
7.0.1 2011-09-29
  • Fixed a rare issue where some users could find one or more of their add-ons hidden after a Firefox update
8.0 2011-11-08 8.0
  • Add-ons installed by third-party programs are now disabled by default
  • Added a one-time add-on selection dialog to manage previously installed add-ons
  • Added Twitter to the search bar
  • Added a preference to load tabs on demand, improving start-up time when windows are restored
  • Improved performance and memory handling when using
  • Added Cross-Origin Resource Sharing (CORS) support for cross-domain textures in WebGL
  • Added support for HTML5 context menus
  • Added support for insertAdjacentHTML()
  • Improved CSS hyphen support for many languages
  • Improved WebSocket support
  • Fixed several stability issues
8.0.1 2011-11-21
  • Fixed Mac OS X crash that occurred in certain instances when a Java Applet is loaded with Java SE 6 version 1.6.0_29 installed.
  • Fixed Windows startup crash caused by RoboForm versions older than 7.6.2.
9.0 2011-12-20 9.0
  • Added type inference, significantly improving JavaScript performance.
  • Improved theme integration for Mac OS X Lion.
  • Added two finger swipe navigation for Mac OS X Lion.
  • Added support for querying Do Not Track status via JavaScript.
  • Added support for the font-stretch CSS property.
  • Improved support for the text-overflow CSS property.
  • Improved standards support for HTML5, MathML, and CSS.
  • Fixed several stability issues.
9.0.1 2011-12-21
  • Fixed crash on Windows, Mac and Linux
10.0 2012-01-31 10.0
  • Most add-ons are now compatible with new versions of Firefox by default.
  • Anti-Aliasing for WebGL is now implemented.
  • CSS3 3D-Transforms are now supported.
  • New element for bi-directional text isolation, along with supporting CSS properties.
  • Full Screen APIs allow you to build a web application that runs full screen.
10.0.1 2012-02-10
  • Security fix.
10.0.2 2012-02-16
  • Fixed Java applets that sometimes caused text input to become unresponsive.
10.0.3esr 2012-03-13
  • Security fixes.
  • Fixed web workers running out of memory, affecting some add-ons used by organizations.
10.0.4esr 2012-04-24
  • Fixed an issue in Firefox ESR 10.0.3 that caused the "Whats New" page to open after an update.
  • Fixed extensions.checkCompatibility.* prefs not working in ESR releases.
10.0.5esr 2012-06-05
  • Fixed the 10.0.5 Firefox top crash with signature [@ GLEngine@0x620cf ].
10.0.6esr 2012-07-17
  • Security fixes.
  • Stability fixes.
  • Fixed some text editing inconsistencies.
10.0.7esr 2012-08-28
  • Fixed contenteditable breaks in 10.0.7 that middle-click to open links
  • Addressed a fix that allows specifying wildcard that matches all simple netbiosnames in network.automatic-ntlm-auth.trusted-uris.
10.0.8esr 2012-10-09
  • Security fixes.
10.0.9esr 2012-10-12
  • Security fix.
10.0.10esr 2012-10-26
  • Security fix.
10.0.11esr 2012-11-20
  • Security fix.
10.0.12esr 2013-01-08
  • Security fix.
11.0 2012-03-13 11.0
  • Migration of settings from Google Chrome
  • SPDY protocol support (disabled by default)
  • RFC 6455 WebSocket protocol support with a unprefixed API
  • Page Inspector Tilt (3D View)
  • Sync Add-ons
  • Redesigned HTML5 video controls
  • Style Editor (CSS)
12.0 2012-04-24 12.0
  • Windows: Firefox is now easier to update with one less prompt (User Account Control)
  • Reintroduced on-demand loading of pinned tabs after restoring a session
  • Page Source now has line numbers
  • Line breaks are now supported in the title attribute
  • Improvements to "Find in Page" to centre search result
  • URLs pasted into the download manager window are now automatically downloaded
  • Support for the text-align-last CSS property has been added
  • Experimental support for ECMAScript 6 Map and Set objects has been implemented
  • Various security fixes
  • Many bug fixes
    • Some TinyMCE-based editors failed to load (739141)
    • OS X: WebGL performance may be degraded on some hardware (713305)
13.0 2012-06-05 13.0
  • When opening a new tab, users are now presented with their most visited pages
  • The default home page now has quicker access to bookmarks, history, settings, and more
  • SPDY protocol now enabled by default for faster browsing on supported sites
  • Restored background tabs are not loaded by default for faster startup
  • Smooth scrolling is now enabled by default
  • 72 total improvements to Page Inspector, HTML panel, Style Inspector, Scratchpad and Style Editor
  • The column-fill CSS property has been implemented
  • Experimental support for ECMAScript 6 Map and Set objects has been implemented
  • Support for the CSS3 background-position property extended syntax has been added
  • The :invalid pseudo-class can now be applied to the element
  • The CSS turn angle unit is now supported
13.0.1 2012-06-15
  • Fixed an issue when Windows Messenger did not load in Hotmail, and the Hotmail inbox did not auto-update
  • Fixed the Hebrew text that was sometimes rendered incorrectly
  • Fixed an issue in Adobe Flash 11.3 that sometimes caused a crash on quit
  • Various security fixes
14.0 2012-06-26 14.0
  • Google searches now utilize HTTPS
  • Full screen support for Mac OS X Lion implemented
  • Plugins can now be configured to only load on click (about:config)
  • The Awesome Bar now auto-completes typed URLs
  • Improved site identity manager, to prevent spoofing of an SSL connection with favicons
  • Pointer Lock API implemented
  • New API to prevent your display from sleeping
  • New text-transform and font-variant CSS improvements for Turkic languages and Greek
  • Long URLs now extend the status bar almost to the whole width of the viewport.
  • Gstreamer backend for HTML5 video to allow H.264 playback (needs to be enabled at compile time).
14.0.1 2012-07-17
  • Various security fixes
  • Fixed the GIF animation that can get stuck when src and image size are changed
  • Mac OSX: Fixed the nsCocoaWindow::ConstrainPosition that uses wrong screen in multi-display setup
  • Fixed the CSS :hover regression when an element's class name is set by Javascript
15.0 2012-08-28 15.0
  • Silent update: Background updates
  • Support for SPDY networking protocol v3
  • WebGL enhancements, including compressed textures for better performance
  • Localization in Maithili
  • Optimized memory usage for add-ons
  • JavaScript debugger integrated into developer tools
  • New layout view added to Inspector
  • High precision event timer implemented
  • The CSS word-break property has been implemented
  • New responsive design tool allows web developers to switch between desktop and mobile views of sites
  • Native support for the Opus audio format added
  • The
  • The source element now supports the media attribute
  • Fixed the focus rings that keep growing when repeatedly tabbing through elements
15.0.1 2012-09-06
  • Addressed a fix where sites visited while in Private Browsing mode could be found through manual browser cache inspection
16.0 2012-10-09 16.0
  • Firefox on Mac OS X now has preliminary VoiceOver support turned on by default
  • Initial web app support (Windows/Mac/Linux)
  • Acholi and Kazakh localizations added
  • Improvements around JavaScript responsiveness through incremental garbage collection
  • New Developer Toolbar with buttons for quick access to tools, error count for the Web Console, and a new command line for quick keyboard access
  • CSS3 Animations, Transitions, Transforms and Gradients unprefixed
  • Recently opened files list in Scratchpad implemented
  • Fixed an issue where debugger breakpoints do not catch on page reload
  • No longer supporting MD5 as a hash algorithm in digital signatures
  • Opus support by default
  • Reverse animation direction has been implemented
  • Per tab reporting in about:memory
  • User Agent strings for pre-release Firefox versions now show only major version
16.0.1 2012-10-11
  • Fixed security vulnerabilities
16.0.2 2012-10-26
  • Fixed security vulnerability
17.0 2012-11-20 17.0
  • First revision of the Social API and support for Facebook Messenger
  • Click-to-play blocklisting implemented to prevent vulnerable plugin versions from running without the user's permission
  • Updated Awesome Bar experience with larger icons
  • Mac OS X 10.5 is no longer supported
  • JavaScript Maps and Sets are now iterable
  • SVG FillPaint and StrokePaint implemented
  • Improvements that make the Web Console, Debugger and Developer Toolbar faster and easier to use
  • New Markup panel in the Page Inspector allows easy editing of the DOM
  • Sandbox attribute for iframes implemented, enabling increased security
  • Over twenty performance improvements, including fixes around the New Tab page
  • Fixed pointer lock that doesn't work in web apps
  • Fixed page scrolling on sites with fixed headers
17.0.1 2012-11-30
  • Reverted user agent change causing some website incompatibilities
  • Fixed font rendering issue
17.0.2esr 2013-01-08
  • Security and stability fixes.
  • Fixed improvements to the Click-to-Play vulnerable plugin blocklisting feature
17.0.3esr 2013-02-19
  • Security fix.
17.0.4esr 2013-03-07
  • Security fix.
17.0.5esr 2013-04-02
  • Security fix.
17.0.6esr 2013-05-14
  • Security fix.
18.0 2013-01-08 18.0
  • Faster JavaScript performance via IonMonkey compiler
  • Support for Retina Display on OS X 10.7 and up
  • Preliminary support for WebRTC
  • Better image quality with Mozilla's new HTML scaling algorithm
  • Performance improvements around tab switching
  • Support for new DOM property window.devicePixelRatio
  • Improvement in startup time through smart handling of signed extension certificates
  • Support for W3C touch events implemented, taking the place of MozTouch events
  • Disable insecure content loading on HTTPS pages
  • Improved responsiveness for users on proxies
18.0.1 2013-01-18
  • Fixed problems involving HTTP Proxy Transactions
  • Fixed unity player crashes on Mac OS X
  • Disabled HIDPI support on external monitors to avoid rendering glitches
18.0.2 2013-02-05
  • Fixed JavaScript related stability issues
19.0 2013-02-19 19.0
  • Built-in PDF Viewer
  • Canvas elements can export their content as an image blob using canvas.toBlob()
  • Startup performance improvements
  • Debugger now supports pausing on exceptions and hiding non-enumerable properties
  • Remote Web Console is available for connecting to Firefox on Android or Firefox OS (experimental, set devtools.debugger.remote-enabled to true)
  • There is now a Browser Debugger available for add-on and browser developers (experimental, set to true)
  • Web Console CSS links now open in the Style Editor
  • CSS @page is now supported
  • CSS viewport-percentage length units implemented (vh, vw, vmin and vmax)
  • CSS text-transform now supports full-width
  • Fixed certain valid WebGL drawing operations that were incorrectly rejected, leaving incomplete rendering in affected pages
  • Fixed an issue that starting Firefox with -private flag incorrectly claims you are not in Private Browsing mode
  • Fixed plugins that stop rendering when the top half of the plugin is scrolled off the top of the page, in HiDPI mode
19.0.1 2013-02-27
  • Windows 8 only: Fixed stability issue for some AMD Radeon HD graphics cards
19.0.2 2013-03-07
  • Security-driven release
20.0 2013-04-02 20.0
  • Security fixes
  • Per-window Private Browsing
  • New download experience
  • Ability to close hanging plugins, without the browser hanging
  • Continued performance improvements around common browser tasks (page loads, downloads, shutdown, etc.)
  • Continued implementation of draft ECMAScript 6 - clear() and Math.imul
  • New JavaScript Profiler tool
  • getUserMedia implemented for web access to the user's camera and microphone (with user permission)
  • now supports blend modes
  • Various
  • Fixed: Details button on Crash Reporter
  • Fixed: Unity plugin that doesn't display in HiDPI mode
20.0.1 2013-04-11
  • Windows-only update to handle issues around handling UNC paths
21.0 2013-05-14 21.0
  • The Social API now supports multiple providers
  • Enhanced three-state UI for Do Not Track (DNT)
  • Preliminary implementation of Firefox Health Report
  • Firefox will suggest how to improve your application startup time if needed
  • Ability to Restore removed thumbnails on New tab Page
  • CSS -moz-user-select:none selection changed to improve compatibility with -webkit-user-select:none
  • Graphics related performance improvements
  • Removed E4X support from SpiderMonkey
  • Implemented Remote Profiling
  • Integrated, Add-on SDK loader and API libraries into Firefox
  • Added support for
  • Implemented scoped stylesheets
  • Fixed: Some function keys may not work when pressed
  • Fixed: Browsing and Download history clearing needs unification to avoid confusion on clearing download history
  • Security fixes
Version Release date Gecko
Release notes

Platform support

Firefox running on a digital advertising sign (identifiable by its connection failure message)

Mozilla provides development builds of Firefox in the following channels: "Beta", "Aurora", and "Nightly". As of May 2013, Firefox 22 beta is in the "Beta" channel, Firefox 23 alpha is in the "Aurora" channel, and Firefox 24 pre-alpha is in the "Nightly" channel.

Features planned for future versions include silent updating so that version increments will not bother the user, although the user will be able to disable that function.

Firefox for mobile

Firefox for mobile 14.0 on Android

Firefox for mobile, codenamed Fennec, is a web browser for smaller non-PC devices, mobile phones and PDAs. It was first released for the Nokia Maemo operating system (specifically the Nokia N900) on January 28, 2010. Version 4 for Android and Maemo was released on March 29, 2011. The browser's version number was bumped from version 2 to version 4 to synchronize with all future desktop releases of Firefox since the rendering engines used in both browsers are the same. Version 7 was the last release for Maemo on the N900. The user interface is completely redesigned and optimized for small screens, the controls are hidden away so that only the web content is shown on screen, and it uses touchscreen interaction methods. It includes the Awesomebar, tabbed browsing, Add-on support, password manager, location-aware browsing, and the ability to synchronize with the user's computer Firefox browser using Firefox Sync.

Extended Support Release

Firefox ESR is a version of Firefox for organizations and other adopters who need extended support for mass deployments. Unlike the regular ("rapid") releases, the ESR will be updated with new features and performance enhancements annually, receiving regular security updates during the year.

CPU architecture

Native 64-bit builds are officially supported on Linux and OS X, but not on Windows:

Operating system 32-bit support 64-bit support
Linux[a] Yes
OS X[b] Yes
Windows[c] Yes No


  • a) Linux: Mozilla made Firefox for 64-bit Linux a priority with the release of Firefox 4, labeling it as tier 1 priority. Since being labeled tier 1, Mozilla has been providing official 64-bit releases for its browser for Linux. Vendor-backed 64-bit support has existed for Linux distributions such as Novell-Suse Linux, Red Hat Enterprise Linux, and Ubuntu prior to Mozilla's support of 64-bit, even though vendors were faced with the challenge of having to turn off the 64-bit JIT compiler due to its instability prior to Firefox 4.
  • b) OS X: The official releases of Firefox for OS X are universal builds that include both 32-bit and 64-bit versions of the browser in one package, and have been this way since Firefox 4. A typical browsing session uses a combination of the 64-bit browser process and a 32-bit plugin process, because some popular plugins still are 32-bit.
  • c) Windows: The 32-bit and 64-bit versions of Windows Vista and Windows 7 can be used to run 32-bit Firefox. Mozilla does not currently support Win64 because many plug-ins do not yet support Win64 and other issues. Mozilla provided 64-bit versions for their Firefox nightly builds until January 8, 2013, but were never considered stable by Mozilla.

System requirements

Browsers compiled from Firefox source code may run on various operating systems; however, officially distributed binaries are meant for the following: Microsoft Windows (XP SP2/SP3, Server 2003, Vista, 7 or 8), OS X 10.6 or higher, and Linux (with the following libraries installed: GTK+ 2.10 or higher, GLib 2.12 or higher, Pango 1.14 or higher, X.Org 1.0 or higher (1.7 or higher is recommended), libstdc++ 4.3 or higher).

Recommended Hardware Windows OS X
Processor Pentium 4 or newer with SSE2 Any Intel processor
Memory (RAM) 512  MB
Hard Drive (free space) 200  MB
Operating system Latest stable version Support status
Microsoft Windows XP / 2003 / Vista /
2008 / 7 / 2008R2 / 8 / 2012
21.0 2004–present
2000 10.0.12esr and 12.0 2004–2013
NT 4 / 98 / ME 2004–2008
95 2004–2007
OS X 10.6 – 10.8 21.0 2009–present
10.5 (Intel) 10.0.12esr and 16.0.2 2007–2013
10.4 – 10.5 (PPC) 3.6.28 2005–2012
10.2 – 10.3 2004–2008
10.0 – 10.1 1.0.8 2004–2006
Linux kernel 2.2.14 and newer
(with some libraries)
21.0 2004–present


  • Firefox 3.5.9 is the last version to work on HP-UX 11i, as packaged by Hewlett-Packard.
  • Firefox 2.0 has been ported to RISC OS (i.e. not supported by Mozilla).



The Mozilla Corporation's relationship with Google has been noted in the popular press, especially with regard to their paid referral agreement. Mozilla's original search deal with Google expired in 2011, but a new deal was struck, where Google agreed to pay Mozilla just under a billion dollars over three years in exchange for the browser to leave Google as its default search engine. The price was driven up due to aggressive bidding from Microsoft's Bing search engine, and Yahoo!'s presence in the auction as well. Despite the deal, Mozilla Firefox maintains relationships with Bing, Yahoo!, Yandex, and eBay.

In 2005, the Mozilla Foundation and Mozilla Corporation had a combined revenue of US$52.9 million, with approximately 95% derived from search engine royalties. In 2006, the Mozilla Foundation and Mozilla Corporation had a combined revenue of US$66.9 million, with approximately 90% derived from search engine royalties. In 2007, the Mozilla Foundation and Mozilla Corporation had a combined revenue of US$81 million, with 88% of this sum (US$66 million) from Google. In 2008, both Mozilla organizations had a combined revenue of US$78.6 million, with 91% coming from Google. In 2009, Google accounted for 86% of Mozilla's revenue, and in 2010, Google was responsible for 84% of Mozilla's $123 million in revenue that year.

The release of the anti-phishing protection in Firefox 2 in particular raised considerable controversy: anti-phishing protection enabled by default is based on a list updated by twice-hourly downloads to the user's computer from Google's server. The user cannot change the data provider within the GUI, and is not informed who the default data provider is. The browser also sends Google's cookie with each update request. Some internet privacy advocacy groups have expressed concerns surrounding Google's possible uses of this data, especially that Firefox's privacy policy states that Google may share information (that is not personally identifying) gathered with "safebrowsing" service with third parties, including business partners.

Following Google CEO Eric Schmidt's comments in December 2009 regarding privacy during a CNBC show, Asa Dotzler, Mozilla's director of community development suggested that users use the Bing search engine instead of Google search. Google also promoted Firefox through YouTube until the release of Google Chrome. In August 2009, Mozilla Security assisted Google by pointing out a security flaw in Google's Chrome browser.


Microsoft's head of Australian operations, Steve Vamos, stated in late 2004 that he did not see Firefox as a threat and that there was not significant demand for the feature-set of Firefox among Microsoft's users. Microsoft Chairman Bill Gates has used Firefox, but has commented that "it's just another browser, and IE [Microsoft's Internet Explorer] is better".

A Microsoft SEC filing on June 30, 2005 acknowledged that "competitors such as Mozilla offer software that competes with the Internet Explorer Web browsing capabilities of our Windows operating system products." The release of Internet Explorer 7 was fast tracked, and included functionality that was previously available in Firefox and other browsers, such as tabbed browsing and RSS feeds.

Despite the cold reception from Microsoft's top management, the Internet Explorer development team maintains a relationship with Mozilla. They meet regularly to discuss web standards such as extended validation certificates. In 2005, Mozilla agreed to allow Microsoft to use its Web feed logo in the interest of common graphical representation of the Web feeds feature.

In August 2006, Microsoft offered to help Mozilla integrate Firefox with the then-forthcoming Windows Vista, an offer Mozilla accepted.

In October 2006, as congratulations for a successful ship of Firefox 2, the Internet Explorer 7 development team sent a cake to Mozilla. As a nod to the browser wars, some jokingly suggested that Mozilla send a cake back along with the recipe, in reference to the open-source software movement. The IE development team sent another cake on June 17, 2008, upon the successful release of Firefox 3, again on March 22, 2011, for Firefox 4, and yet again for the Firefox 5 release.

In November 2007, Jeff Jones (a "security strategy director" in Microsoft's Trustworthy Computing Group) criticized Firefox, claiming that Internet Explorer experienced fewer vulnerabilities and fewer higher severity vulnerabilities than Firefox in typical enterprise scenarios. Mozilla developer Mike Shaver discounted the study, citing Microsoft's bundling of security fixes and the study's focus on fixes, rather than vulnerabilities, as crucial flaws.

In February 2009, Microsoft released Service Pack 1 for version 3.5 of the .NET Framework. This update also installed Microsoft .NET Framework Assistant add-on (enabling ClickOnce support). The update received media attention after users discovered that the add-on could not be uninstalled through the add-ons interface. Several hours after the website posted an article regarding this update, Microsoft employee Brad Abrams posted in his blog Microsoft's explanation for why the add-on was installed, and also included detailed instructions on how to remove it. However, the only way to get rid of this extension was to modify manually the Windows Registry, which could cause Windows systems to fail to boot up if not done correctly.

On October 16, 2009, Mozilla blocked all versions of Microsoft .NET Framework Assistant from being used with Firefox and from the Mozilla Add-ons service. Two days later, the add-on was removed from the blocklist after confirmation from Microsoft that it is not a vector for vulnerabilities. Version 1.1 (released on June 10, 2009 to the Mozilla Add-ons service) and later of the Microsoft .NET Framework Assistant allows the user to disable and uninstall in the normal fashion.

Firefox is one of the twelve browsers offered to European Economic Area users of Microsoft Windows since 2010 – see

IRS audit

The IRS opened an audit of the Mozilla Foundation's 2004-5 revenues in 2008, due to its search royalties, and in 2009, the investigation was expanded to the 2006 and 2007 tax years, though that part of the audit was closed. As Mozilla does not derive at least a third of its revenue from public donations, it does not automatically qualify as a public charity.

In November 2012, the audit was closed after finding that the Mozilla Foundation owed a settlement of $1.5 million dollars to the IRS.

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