Mozilla Firefox (or simply Firefox) is a free and open-source[23] web browser developed by The Mozilla Foundation and its subsidiary, Mozilla Corporation. Firefox is available for Microsoft Windows, macOS, Linux, BSD,[8][9][10] illumos[11] and Solaris[13] operating systems. Its sibling, Firefox for Android, is also available. Firefox uses the Gecko layout engine to render web pages, which implements current and anticipated web standards.[24] In 2017, Firefox began incorporating new technology under the code name Quantum to promote parallelism and a more intuitive user interface.[25] An additional version, Firefox for iOS, was released on November 12, 2015. Due to platform restrictions, it uses the WebKit layout engine instead of Gecko, as with all other iOS web browsers.

Firefox was created in 2002 under the codename "Phoenix" by the Mozilla community members who desired a standalone browser, rather than the Mozilla Application Suite bundle. During its beta phase, Firefox proved to be popular with its testers and was praised for its speed, security, and add-ons compared to Microsoft's then-dominant Internet Explorer 6. Firefox was released on November 9, 2004,[26] and challenged Internet Explorer's dominance with 60 million downloads within nine months.[27] Firefox is the spiritual successor of Netscape Navigator, as the Mozilla community was created by Netscape in 1998 before their acquisition by AOL.[28]

Firefox usage grew to a peak of 32% at the end of 2009,[29] with version 3.5 overtaking Internet Explorer 7, although not Internet Explorer as a whole.[30][31] Usage then declined in competition with Google Chrome.[29] As of January 2019, Firefox has 9.5% usage share as a "desktop" browser, according to StatCounter, making it the second-most popular such web browser;[32] usage across all platforms is lower at 4.66% (and then third-most popular overall).[33] Firefox is still the most popular desktop browser in a few countries including Cuba (even most popular overall at 49.7%[34]) and Eritrea with 72.26%[35] and 83.28%[36] of the market share, respectively. According to Mozilla, in December 2014, there were half a billion Firefox users around the world.[37]

Mozilla Firefox
Firefox Logo, 2017
Customized Firefox 57 (Quantum) running on Windows 10
Customized Firefox 57 (Quantum) running on Windows 10
Initial releaseSeptember 23, 2002
Stable release(s) [±]
Standard66.0.3 / April 10, 2019[1]
Extended Support Release60.6.1 / March 22, 2019[2]
Preview release(s) [±]
Beta & Developer Edition67.0beta / March 19, 2019[3][4]
Nightly68.0a1 / March 18, 2019[5][6]
Written inC++, JavaScript, HTML, C, Rust[7]
Operating system
Included withVarious Unix-like operating systems
EnginesGecko, Quantum, SpiderMonkey
  • Linux, IA-32: 58.2 MB[15]
  • Linux, x64: 56.6 MB[16]
  • macOS: 62.2 MB[17]
  • Windows, IA-32: 40.8 MB[18]
  • Windows, x64: 42.7 MB[19]
Standard(s)HTML5, CSS3
Available in90 languages[20]
TypeWeb browser
LicenseMPL 2.0[21][22]


The 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.[38] 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.[39] On April 3, 2003, the Mozilla Organization announced that they planned to change their focus from the Mozilla Suite to Firefox and Thunderbird.[40] The community-driven SeaMonkey was formed and eventually replaced the Mozilla Application Suite in 2005.

Phoenix 0.1
Phoenix 0.1 screenshot on Windows XP

The Firefox project has undergone several name changes.[41][42][43][44][45][46][47][48] It was originally titled Phoenix, which carried the implication of the mythical firebird that rose triumphantly from the ashes of its dead predecessor, in this case from the "ashes" of Netscape Navigator after it had been killed off by Microsoft Internet Explorer in the "First Browser War". Phoenix was renamed due to trademark issues with Phoenix Technologies; the replacement name, Firebird, provoked an intense response from the Firebird database software project.[49][50] In response, the Mozilla Foundation stated that the browser would always bear the name Mozilla Firebird to avoid confusion. After further pressure, on February 9, 2004, Mozilla Firebird became Mozilla Firefox.[51] The name Firefox was said to be derived from a nickname of the red panda,[52][53] which became the mascot for the newly named project. For the abbreviation of Firefox, Mozilla prefers Fx or fx, though it is often abbreviated as FF.[54] The Firefox project went through many versions before version 1.0 was released on November 9, 2004.[55]

In 2016, Mozilla announced a project known as Quantum, which sought to improve Firefox's Gecko engine and other components to improve Firefox's performance, modernize its architecture, and transition the browser to a multi-process model. These improvements came in the wake of decreasing market share to Google Chrome, as well as concerns that its performance was lapsing in comparison. Despite its improvements, these changes required existing add-ons for Firefox to be made incompatible with newer versions, in favor of a new extension system that is designed to be similar to Chrome and other recent browsers. Firefox 57, which was released in November 2017, was the first version to contain enhancements from Quantum, and has thus been named Firefox Quantum. A Mozilla executive stated that Quantum was the "biggest update" to the browser since version 1.0.[56][57][58]


Features include tabbed browsing, spell checking, incremental search, live bookmarking, Smart Bookmarks, a download manager, private browsing, location-aware browsing (also known as "geolocation") based on a Google service,[59] and an integrated search system, which uses Google by default in most markets.[60] 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 and more recently there has been an integration feature with Pocket. Firefox Hello was an implementation of WebRTC, added in October 2014, which allows users of Firefox and other compatible systems to have a video call, with the extra feature of screen and file sharing by sending a link to each other. Firefox Hello was scheduled to be removed in September 2016.[61]

Functions can be added through add-ons created by third-party developers. Add-ons are primarily coded using an HTML and JavaScript API known as WebExtensions, which is designed to be similar to the Google Chrome and Microsoft Edge extension systems. Firefox previously supported add-ons using the XUL and XPCOM APIs, which allowed them to directly access and manipulate much of the browser's internal functionality. As they are not compatible with its multi-process architecture, XUL add-ons are now deemed Legacy add-ons and are no longer supported on Firefox 57 and newer.[62][63]

Firefox can have themes added to it, which users can create or download from third parties to change the appearance of the browser. The Firefox add-on website also gives users the ability to add other applications such as games, ad-blockers, screenshot apps, and many other apps.[64][65]


Acid3 Mozilla Firefox test
The result of the Acid3 test on Firefox 17

Firefox implements many web standards, including HTML4 (almost full HTML5), XML, XHTML, MathML, SVG 2 (partial),[66][67] CSS (with extensions),[68] ECMAScript (JavaScript), DOM, XSLT, XPath, and APNG (Animated PNG) images with alpha transparency.[69] Firefox also implements standards proposals created by the WHATWG such as client-side storage,[70][71] and canvas element.[72] These standards are implemented through the Gecko layout engine, and SpiderMonkey JavaScript engine.

Firefox has passed the Acid2 standards-compliance test since version 3.0.[73] 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.[74] Because the SVG font tests were removed from the Acid3 test in September 2011, Firefox 4 and greater scored 100/100.[75][76]

Firefox also implements "Safe Browsing",[77] a proprietary protocol[78] from Google used to exchange data related with phishing and malware protection.

Since version 38 on Windows Vista and newer, Firefox supports the playback of video content protected by HTML5 Encrypted Media Extensions (EME). For security and privacy reasons, EME is implemented within a wrapper of open source code that allows execution of a proprietary DRM module by Adobe Systems—Adobe Primetime Content Decryption Module (CDM). CDM runs within a "sandbox" environment to limit its access to the system, and provide it a randomized device ID to prevent services from uniquely identifying the device for tracking purposes. The DRM module, once it has been downloaded, is enabled and disabled in the same manner as other plug-ins. Since version 47,[79] "Google's Widevine CDM on Windows and Mac OS X so streaming services like Amazon Video can switch from Silverlight to encrypted HTML5 video" is also supported.

Firefox downloads and enables the Adobe Primetime and Google Widevine CDMs by default to give users a smooth experience on sites that require DRM. Each CDM runs in a separate container called a sandbox and you will be notified when a CDM is in use. You can also disable each CDM and opt out of future updates

— Watch DRM content on Firefox[80]

and that it is "an important step on Mozilla's roadmap to remove NPAPI plugin support."[81] Upon the introduction of EME support, builds of Firefox on Windows were also introduced that exclude support for EME.[82][83]

On the HTML5 web standards test, Firefox 65 scores 520 out of 582 points.[84]


Firefox allowed for a sandbox security model to manage privileges accorded to JavaScript code, but that feature has since been deprecated.[85] It limits scripts from accessing data from other websites based on the same-origin policy.[86] It also provides support for smart cards to web applications, for authentication purposes.[87] It uses TLS to protect communications with web servers using strong cryptography when using the HTTPS protocol.[88] The freely available HTTPS Everywhere add-on enforces HTTPS, even if a regular HTTP URL is entered. Firefox now supports HTTP/2.[89]

The Mozilla Foundation offers a "bug bounty" (US$3,000 to US$7,500 cash reward) to researchers who discover severe security holes in Firefox.[90] Official guidelines for handling security vulnerabilities discourage early disclosure of vulnerabilities so as not to give potential attackers an advantage in creating exploits.[91]

Because Firefox generally has fewer publicly known 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.[92][93][94][95] The Washington Post reported that exploit code for known critical 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 nine days before Mozilla issued a patch to remedy the problem.[96]

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, with Firefox's vulnerabilities being fixed on average one day after the exploit code was made available, as compared to nine days for Internet Explorer.[97] Symantec later clarified their statement, saying that Firefox still had fewer security vulnerabilities than Internet Explorer, as counted by security researchers.[98]

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 fifth-most vulnerable desktop software, with Internet Explorer as the eighth, and Google Chrome as the first.[99]

InfoWorld has cited security experts saying that, as Firefox becomes more popular, more vulnerabilities will be found,[100] 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," she said.[101]

In October 2009, Microsoft's security engineers acknowledged that Firefox was vulnerable to a security issue found in the 'Windows Presentation Foundation' browser plug-in since February of that year. A .NET Framework 3.5 SP1 Windows Update had silently installed the vulnerable plug-in into Firefox.[102] This vulnerability has since been patched by Microsoft.[103]

As of February 11, 2011, Firefox 3.6 had no known unpatched security vulnerabilities according to Secunia.[104] Internet Explorer 8 had five unpatched security vulnerabilities, the worst being rated "Less Critical" by Secunia.[105] Mozilla claims that all patched vulnerabilities of Mozilla products are publicly listed.[106]

On January 28, 2013, Mozilla was recognized as the most trusted internet company for privacy in 2012.[107] This study was performed by the Ponemon Institute and was a result of a survey from more than 100,000 consumers in the United States.

In February 2013, plans were announced for Firefox 22 to disable third-party cookies by default. However, the introduction of the feature was then delayed so Mozilla developers could "collect and analyze data on the effect of blocking some third-party cookies." Mozilla also collaborated with Stanford University's "Cookie Clearinghouse" project to develop a blacklist and whitelist of sites that will be used in the filter.[108][109]

Version 23, released in August 2013, followed the lead of its competitors by blocking iframe, stylesheet, and script resources served from non-HTTPS servers embedded on HTTPS pages by default. Additionally, JavaScript could also no longer be disabled through Firefox's preferences, and JavaScript was automatically re-enabled for users who upgraded to 23 or higher with it disabled. The change was made due to its use across the majority of websites, the potential repercussions on non-experienced users who are unaware of its impact, along with the availability of extensions such as NoScript, which can disable JavaScript in a more controlled fashion. The following release added the ability to disable JavaScript through the developer tools for testing purposes.[110][111][112]

In January 2015, TorrentFreak reported that using Firefox when connected to the internet using a VPN can be a serious security issue due to the browser's support for WebRTC.[113]

Beginning with Firefox 44, all extensions must be signed by Mozilla to be used in release and beta versions of Firefox. Firefox 43 blocked unsigned extensions, but allowed enforcement of extension signing to be disabled. All extensions must be submitted to Mozilla Add-ons and be subject to code analysis in order to be signed, although extensions do not have to be listed on the service in order to be signed.[114][115]

In Firefox versions prior to 7.0, an information bar appears on the browser's first start asking users whether they would like to send performance statistics, or "telemetry", to Mozilla. It is enabled by default in development versions of Firefox, but not in release versions.[116] According to Mozilla's privacy policy,[117] these statistics are stored only in aggregate format, and the only personally identifiable information transmitted is the user's IP address.

Until November 2018, Firefox was the last widely used browser not to use a browser sandbox to isolate Web content in each tab from each other and from the rest of the system.[118][119]

Since version 60 Firefox includes the option to use DNS over HTTPS (DoH), which causes DNS lookup requests to be sent encrypted over the HTTPS protocol. To use this feature the user must set certain preferences beginning with "network.trr" (Trusted Recursive Resolver) in about:config: if network.trr.mode is 0, DoH is disabled; 1 activates DoH in addition to unencrypted DNS; 2 causes DoH to be used before unencrypted DNS; to use only DoH, the value must be 3. By setting network.trr.uri to the URL special Cloudflare servers will be activated.[120] Mozilla has a privacy agreement with this server host that restricts their collection of information about incoming DNS requests.[121]


Firefox is a widely 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 and Simplified Chinese characters.[122] As of April 2019, currently supported versions 66.0.3 and 60.6.1esr are available in 89 locales (79 languages).[20]

Platform availability

The desktop version of Firefox is available and supported for Microsoft Windows, macOS and Linux, while Firefox for Android is available for Android (formerly Firefox for mobile, it also ran on Firefox OS).

Operating system Latest stable version Support status
Windows 7 and later, Server 2008 R2 and later Current stable version: 66.0.3 (x64)[123] 2015–
Older version, yet still supported: 60.6.1esr (x64)[124]
Current stable version: 66.0.3 (IA-32) 2009–
Older version, yet still supported: 60.6.1esr (IA-32)
XP SP2 and SP3, Vista,
Server 2003, and Server 2008
Old version, no longer supported: 52.9.0esr (IA-32) 2004–2018
Old version, no longer supported: 52.0.2 (IA-32)[125] 2004–2017
2000, XP RTM and SP1 Old version, no longer supported: 10.0.12esr 2004–2013
Old version, no longer supported: 12.0[126] 2004–2012
NT 4 (IA-32), 98 and ME Old version, no longer supported: 2004–2008
95 Old version, no longer supported: 2004–2007
macOS 10.910.14 Current stable version: 66.0.3[123] 2013–
Older version, yet still supported: 60.6.1esr[124]
10.610.8 Old version, no longer supported: 45.9.0esr[127] 2009–2017
Old version, no longer supported: 47.0.1[128] 2009–2016
10.5 (IA-32,x64) Old version, no longer supported: 10.0.12esr 2007–2013
Old version, no longer supported: 16.0.2[129] 2007–2012
10.4 (IA-32,PPC)–10.5 (PPC) Old version, no longer supported: 3.6.28[130][131] 2005–2012
10.210.3 Old version, no longer supported: 2004–2008
10.010.1 Old version, no longer supported: 1.0.8 2004–2006
Linux desktop Current stable version: 66.0.3 (x64)[123] 2011–
Older version, yet still supported: 60.6.1esr (x64)[124]
Current stable version: 66.0.3 (IA-32) 2004–
Older version, yet still supported: 60.6.1esr (IA-32)


  • In March 2014, the Windows Store app version of Firefox was cancelled, although there is a beta release.[132]
  • SSE2 instruction set support is required for 53.0 and later, IA-32 support only applies to superscalar processors.

Firefox source code may be compiled for various operating systems; however, officially distributed binaries are provided for the following:

Required hardware and software[133]
Requirement Microsoft Windows Linux desktop macOS Android[134] iOS
CPU Pentium 4 or newer with SSE2[135] Any x86-64 CPU[135] ARM and IA-32[135] ARM
Memory (RAM) 512 MB for the 32-bit version and 2 GB for the 64-bit version 384 MB ?
Hard disk drive free space 200 MB 50 MB ?
Operating system 7 or later
Server 2008 R2 or later[133]
OS X 10.9 or newer 4.1 or newer[134] 11.4 or later[137]

Microsoft Windows

Firefox 1.0 was released for Windows 9x, as well as Windows NT 4.0 and later. Some users reported the 1.x builds were operable (but not installable) on Windows NT 3.51.[138]

In September 2013, a Metro-style version of Firefox optimized for touchscreen use was introduced on the "Aurora" release channel. However, the project has since been cancelled as of March 2014, with Mozilla citing a lack of user adoption of the beta versions.[139][140][141]

Version 43.0 included the first x64 builds, made for Windows 7 and Server 2008 R2.[142] Version 49.0 dropped support for processors without the SSE2 instruction set on Windows.

In April 2017, users of Firefox 52.0.2 on Windows XP, Windows Vista, Windows Server 2003 and Windows Server 2008 who had automatic updates enabled were migrated to Firefox 52 ESR. The support was projected to end for these operating systems with the last release in June 2018.[143]


The first official release (Firefox version 1.0) supported macOS (then called Mac OS X) on the PowerPC architecture. Mac OS X builds for the IA-32 architecture became available via a universal binary which debuted with Firefox in 2006.

Starting with version 4.0, Firefox was released for the x64 architecture to which macOS had migrated.[144]


Since its inception, Firefox for Linux supported the 32-bit memory architecture of the IA-32 instruction set. 64-bit builds were introduced in the 4.0 release.[144] The 46.0 release replaced GTK+ 2.18 with 3.4 as a system requirement on Linux and other systems running X.Org.[145] Starting with 53.0, the 32-bit builds require the SSE2 instruction set.

Firefox for mobile

Firefox for Android, codenamed Fennec, is a web browser for smaller non-PC devices, mobile phones, and PDAs. It was originally first released for the Nokia Maemo operating system, specifically the Nokia N900, on January 28, 2010.[146] On March 29, 2011, besides Maemo, Version 4 was added for Android.[147] With the release of mobile version, the browser's version number was bumped from 2 to 4, synchronizing it with all future desktop releases of Firefox because the rendering engines used in both browsers are the same.[148] Version 7 was the last release for Maemo on the N900.[149]

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 Awesome Bar, 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.[150]

In April 2013, then-Mozilla CEO Gary Kovacs said that Firefox would not come to iOS as long as Apple required the use of the WebKit layout engine to do so. One reason given by Mozilla was that prior to iOS 8, Apple had supplied third-party browsers with an inferior version of their JavaScript engine which hobbled their performance, making it impossible to match Safari's JavaScript performance on the iOS platform.[151] Apple later opened their "Nitro" JavaScript engine to third-party browsers.[152] In 2015, Mozilla announced it was moving forward with Firefox for iOS, with a preview release made available in New Zealand in September of that year.[153][154][155] In November 2016, Firefox released a new iOS app titled Firefox Focus, a private web browser.[156]

Operating system Latest stable version Support status
(including Android-x86)
5.0 and later[157] Current stable version: 66.0.2 (ARMv8-A) 2017–
4.1 and later Current stable version: 66.0.2 (IA-32)[158] 2013–
Current stable version: 66.0.2 (ARMv7) 2012–
4.0 Old version, no longer supported: 55.0.2 (IA-32)[158][159] 2013–2017
Old version, no longer supported: 55.0.2 (ARMv7) 2011–2017
3.0–3.2 Old version, no longer supported: 45.0.2 (ARMv7)[158] 2011–2016
2.3 Old version, no longer supported: 47.0 (ARMv7)[158][160] 2011–2016
2.24.3 Old version, no longer supported: 31.3.0esr (ARMv6) 2012–2015
2.2 Old version, no longer supported: 31.0 (ARMv7)[161] 2011–2014
2.1 Old version, no longer supported: 19.0.2 (ARMv6) 2012–2013
Old version, no longer supported: 19.0.2 (ARMv7) 2011–2013
2.0 Old version, no longer supported: 6.0.2 (ARMv7) 2011
Firefox OS 2.2 Old version, no longer supported: 35/36/37 2015
2.1 Old version, no longer supported: 33/34 2014–2015
2.0 Old version, no longer supported: 31/32 2014–2015
Maemo Old version, no longer supported: 7.0 2010–2011
  • Firefox for iOS is not listed in this table as its version numbers would be misleading; it uses version numbers that do not correspond to any of the other Firefox versions. Those share a core component, the Gecko rendering engine, and track its version numbers, whereas the version for the iOS operating system uses the operating system's rendering engine (WebKit), rather than Mozilla's (Gecko).

Unofficial ports

Firefox has also been ported to FreeBSD,[162] NetBSD,[163] OpenBSD,[164] OpenIndiana,[165] OS/2[166] and SkyOS, and an unofficial rebranded version called Timberwolf has been available for AmigaOS 4. An unofficial continuation of the macOS PowerPC release continues as TenFourFox.

The Firefox port for OpenBSD is maintained by Landry Breuil since 2010. Firefox is regularly built for the current branch of the operating system, the latest versions are packaged for each -release and remain frozen until the next release. In 2017, Landry began hosting packages of newer Firefox versions for OpenBSD releases from 6.0 onwards, making them available to installations without the ports system.[167]

The Solaris port of Firefox (including OpenSolaris) was maintained by the Oracle Solaris Desktop Beijing Team,[168][169] until March 2017 when the team was disbanded.[170] There was also an unofficial port of Firefox 3.6.x to IBM AIX[171][172] and of v1.7.x to UnixWare.[173]

Operating system Latest stable version Support status
Solaris 10–11 and OpenSolaris Older version, yet still supported: 60.6.1esr (IA-32,SPARC V9) 2005–
8–9 Old version, no longer supported: (IA-32,SPARC V9) 2004–2008
HP-UX 11i v2–v3 Old version, no longer supported: 3.5.9 (IA-64,PA-RISC)[174] N/A
FreeBSD (DragonFly BSD) 12 Current stable version: 66.0.3 (IA-32) and 66.0.3 (x64) 2018–
Older version, yet still supported: 60.6.1esr (IA-32) and 60.6.1esr (x64)
11 Current stable version: 66.0.3 (IA-32) and 66.0.3 (x64) 2016–
Older version, yet still supported: 60.6.1esr (IA-32) and 60.6.1esr (x64)
OpenBSD 6.4 Older version, yet still supported: 60.6.1esr (IA-32,x64) 2018–
5.8 Old version, no longer supported: 38.7.1esr (PPC) 2015–2016
5.7 Old version, no longer supported: 31.6.0esr (SPARC V9) 2015
5.1 Old version, no longer supported: 3.6.25 (Alpha) N/A


Mozilla Firefox 65

Firefox 65 running on Arch Linux

Firefox 57 High Sierra

Firefox 57 on macOS High Sierra

Mozilla Firefox Developer Edition 63

Firefox Developer Edition on Windows 10

Firefox Android 62

Firefox for Android 62 on Android

Firefox in firefox os

Firefox on Firefox OS

FennecMeeGo (cropped)

Firefox on MeeGo OS

Version history

Besides official releases, Mozilla provides development builds of Firefox in distribution channels named, in order of most to least stable, "Beta", "Developer Edition" (former "Aurora", renamed on November 10, 2014[175][176]), and "Nightly".[177] Starting from Firefox 54, "Developer Edition" is based on the "Beta" build.[178]

Firefox ESR (Extended Support Release) is a version of Firefox for organizations and other groups that need extended support for mass deployments. Each ESR release, based on the regular version released at the same time, is supported for approximately one year.[179] Unlike the regular ("rapid") releases, ESRs are not updated with new features and performance enhancements every six weeks, but rather are updated with only high-risk-reduction or high-impact security fixes or major stability fixes with point releases, until the end of the ESR cycle.[180]


Firefox source code is free software, with most of it being released under the Mozilla Public License (MPL) version 2.0.[22] This license permits anyone to view, modify, or redistribute the source code. As a result, several publicly released applications have been built from it, such as Netscape, Flock, Miro, GNU IceCat, Iceweasel, Songbird, Pale Moon, and Comodo IceDragon.

In the past, Firefox was licensed solely under the MPL, then version 1.1,[181] which the Free Software Foundation criticized for being weak copyleft, as the license permitted, in limited ways, proprietary derivative works. Additionally, code only licensed under MPL 1.1 could not legally be linked with code under the GPL.[182][183] To address these concerns, Mozilla re-licensed most of Firefox under the tri-license scheme of MPL 1.1, GPL 2.0, or LGPL 2.1. 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.[181] However, on January 3, 2012, Mozilla released the GPL-compatible MPL 2.0,[184] and with the release of Firefox 13 on June 5, 2012, Mozilla used it to replace the tri-licensing scheme.[185]

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

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.[186] The name "Firefox" derives from a nickname of the red panda.[52]

Mozilla has placed the Firefox logo files under open-source licenses,[187][188] but its trademark guidelines do not allow displaying altered[189] or similar logos[190] in contexts where trademark law applies.

Iceweasel icon
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.[23] Open source browsers "enable greater choice and innovation in the market rather than aiming for mass-market domination."[191] 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".[192]

To allow distributions of the code without using the official branding, the Firefox build system contains a "branding switch". This switch, often used for alphas ("Auroras") of future Firefox versions, allows the code to be compiled without the official logo and name, and can allow a derivative work unencumbered by restrictions on the Firefox trademark to be produced. In the unbranded build 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 required explicit approval from Mozilla for the changes made to the underlying code, and required the use of all of the official branding. For example, it was 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.[193] Ultimately, Debian switched to branding their modified version of Firefox "Iceweasel" (but in 2016 switched back to Firefox), along with other Mozilla software. GNU IceCat is another derived version of Firefox distributed by the GNU Project, which maintains its own separate branding.[194]

Branding and visual identity

Early Firebird and Phoenix releases of Firefox were considered to have reasonable visual designs, but fell short when compared to many other professional 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.[195]

Shortly afterwards, the Mozilla Foundation invited Garrity 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. Included were new icon designs by silverorange, a group of web developers with a long-standing relationship with Mozilla. The final renderings are by Jon Hicks, who had worked on Camino.[196][197] The logo was later revised and updated, fixing several flaws found when it was enlarged.[198] The animal shown in the logo is a stylized fox, although "firefox" is usually a common name for the red panda. The panda, according to Hicks, "didn't really conjure up the right imagery" and was not widely known.[197]

The Firefox icon is a trademark used to designate the official Mozilla build of the Firefox software and builds of official distribution partners.[199] For this reason software distributors who distribute modified versions of Firefox do not use the icon.

Mozilla Firefox 3.5 logo 256

Firefox 3.5–22 from June 30, 2009 to June 25, 2013

Mozilla Firefox logo 2013

Firefox 23–56, from August 6, 2013 to September 28, 2017[200]

Firefox Logo, 2017

Firefox 57 and later, since November 14, 2017


Minefield logo (former name for "Nightly")

Mozilla Nightly icon 2011

The 2011 Nightly logo, used to represent nightly builds of pre-alpha versions

Mozilla Firefox Nightly logo 2013

The 2013 Nightly logo

Firefox Nightly Logo, 2017

Current Nightly logo

Firefox Developer Edition logo

The 2015 Developer Edition logo

Firefox Developer Edition Logo, 2017

Current Developer Edition logo

Mozilla Aurora icon

The 2011 Aurora logo, used to represent an alpha release

Mozilla Firefox Aurora logo 2013

The 2013 Aurora logo

Mozilla Phoenix logo vector

Logo of "Phoenix" and "Firebird" before being renamed as Firefox

Deer park globe

Blue globe artwork, distributed with the source code, and is explicitly not protected as a trademark[201]


Firefox mascot - FISL 16
Firefox mascot at the FISL 16 (2015), Brazil

Firefox was adopted rapidly, with 100 million downloads in its first year of availability.[202] This was followed by a series of aggressive marketing campaigns starting in 2004 with a series of events Blake Ross and Asa Dotzler called "marketing weeks".[203]

Firefox continued to heavily market itself by releasing a marketing portal dubbed "Spread Firefox" (SFX) on September 12, 2004,[204] It debuted along with the Firefox Preview Release, creating a centralized space for the discussion of various marketing techniques. The release of their manifesto stated that "the Mozilla project is a global community of people who believe that openness, innovation and opportunity are key to the continued health of the Internet."[191] A two-page ad in the edition of December 16 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.[205] 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.[206] This resulted in an official certified Guinness world record, with over eight million downloads.[207] 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."[208]

In celebration of the third anniversary of the founding of the Mozilla Foundation, the "World Firefox Day" campaign was established on July 15, 2006,[209][210] and ran until September 15, 2006.[211] 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.

The Firefox community has also engaged in the promotion of their web browser. In 2006, some of Firefox's contributors from Oregon State University 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.[212] After Firefox reached 500 million downloads on February 21, 2008, the Firefox community celebrated by visiting Freerice to earn 500 million grains of rice.[213]

Other initiatives included Live Chat, a service Mozilla launched in 2007 that allowed users to seek technical support from volunteers.[214] The service was later retired.[215]

To promote the launch of Firefox Quantum in November 2017, Mozilla partnered with Reggie Watts to produce a series of TV ads and social media content.[216]


In December 2005, Internet Week ran an article in which many readers reported high memory usage in Firefox 1.5.[217] 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.[218] Other known causes of memory problems were malfunctioning extensions such as Google Toolbar and some older versions of AdBlock,[219] or plug-ins, such as older versions of Adobe Acrobat Reader.[220] When PC Magazine in 2006 compared memory usage of Firefox 2, Opera 9, and Internet Explorer 7, they found that Firefox used approximately as much memory as each of the other two browsers.[221]

Softpedia noted that Firefox 1.5 took longer to start up than other browsers,[222] which was confirmed by further speed tests.[223]

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.[224] 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.[225][226] 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.[227][228][229] In mid-2009, BetaNews benchmarked Firefox 3.5 and declared that it performed "nearly ten times better on XP than Microsoft Internet Explorer 7".[230]

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.[231]

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 HTML5, Java, JavaScript, DOM, CSS 3, Flash, Silverlight, and WebGL (WebGL 2 is current as of version 51; and Java and Silverlight stop working as of version 52)—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 Google Chrome.[232]

In June 2013, Tom's Hardware again performance tested Firefox 22, Chrome 27, Opera 12, and Internet Explorer 10. They found that Firefox slightly edged out the other browsers in their "performance" index, which examined wait times, JavaScript execution speed, HTML5/CSS3 rendering, and hardware acceleration performance. Firefox also scored the highest on the "non-performance" index, which measured memory efficiency, reliability, security, and standards conformance, finishing substantially ahead of Chrome, the runner-up. Tom's Hardware concluded by declaring Firefox the "sound" winner of the performance benchmarks.[233]

In January 2014, a benchmark testing the memory usage of Firefox 29, Google Chrome 34, and Internet Explorer 11 indicated that Firefox used the least memory when a substantial number of tabs were open.[234]

In benchmark testing in early 2015 on a "high-end" Windows machine, comparing Microsoft Edge, Internet Explorer, Firefox, Chrome, and Opera, Firefox achieved the highest score on three of the seven tests. Four different Javascript performance tests gave conflicting results. Firefox bested the others on the Peacekeeper benchmark, but was behind the Microsoft products when tested with SunSpider. Measured with Mozilla's Kraken, it came second place to Chrome, while on Google's Octane challenge it took third behind Chrome and Opera. Firefox took the lead with WebXPRT, which runs several typical HTML5 and Javascript tasks. Firefox, Chrome, and Opera all achieved the highest possible score on the Oort Online test, measuring WebGL rendering speed (WebGL 2 is now current). In terms of HTML5 compatibility testing, Firefox was ranked in the middle of the group.[235]

A similar set of benchmark tests in 2016 showed Firefox's Javascript performance on Kraken and the newer Jetstream tests trailing slightly behind all other tested browsers except Internet Explorer, which performed relatively poorly. On Octane, Firefox came ahead of IE and Safari, but again slightly behind the rest, including Vivaldi and Microsoft Edge. Edge took overall first place on the Jetstream and Octane benchmarks.[236]

As of the adoption of Firefox 57 and Mozilla's Quantum project entering production browsers in November 2017, Firefox was tested to be faster than Chrome in independent JavaScript tests, and demonstrated to use less memory with many browser tabs opened.[237][238]

Market adoption

Downloads have continued at an increasing rate since Firefox 1.0 was released on November 9, 2004, and as of 31 July 2009 Firefox had already been downloaded over one billion times.[239] This number does not include downloads using software updates or those from third-party websites.[240] 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.

In July 2010, IBM asked all employees (about 400,000) to use Firefox as their default browser.[241]

Firefox was the second-most used web browser until November 2011, when Google Chrome surpassed it.[242] According to Mozilla, Firefox has more than 450 million users as of October 2012.[37][243]

As of April 2018, Firefox was the second-most widely used desktop browser, and that position makes it the fourth-most popular with approximately 11.78% of worldwide usage share of web browsers across all platforms.[244]

Desktop/laptop browser statistics
Google Chrome
Mozilla Firefox
Internet Explorer
Microsoft Edge
Desktop web browser market share according to StatCounter for January 2019.[245]

See also


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Further reading

  • Cheah, Chu Yeow (2005). Firefox Secrets: A Need-To-Know Guide. O'Reilly. ISBN 978-0-9752402-4-3.
  • Feldt, Kenneth C. (2007). Programming Firefox. O'Reilly. ISBN 978-0-596-10243-2.
  • Granneman, Scott (2005). Don't Click on the Blue e!: Switching to Firefox. O'Reilly. ISBN 978-0-596-00939-7.
  • Hofmann, Chris; Marcia Knous; John Hedtke (2005). Firefox and Thunderbird Garage. Prentice Hall PTR. ISBN 978-0-13-187004-8.
  • McFarlane, Nigel (2005). Firefox Hacks. O'Reilly. ISBN 978-0-596-00928-1.
  • Reyes, Mel (2005). Hacking Firefox: More Than 150 Hacks, Mods, and Customizations. Wiley. ISBN 978-0-7645-9650-6.
  • Ross, Blake (2006). Firefox for Dummies. Wiley. ISBN 978-0-471-74899-1.

External links

Add-on (Mozilla)

Add-on is the Mozilla term for software modules that can be added to the Firefox web browser and related applications. There are three types: extensions, themes, and plug-ins. Mozilla hosts them on its official add-on website.In 2017, Mozilla enacted major changes to the application programming interface (API) for add-ons in Firefox. The long-standing XUL and XPCOM capabilities were replaced by an API modeled after Google Chrome's; Firefox extensions are now largely compatible with their Chrome counterparts. Plug-ins were deprecated, with the exception of the Adobe Flash Player.

Basilisk (web browser)

Basilisk is an open-source web browser created by the developers of the Pale Moon browser. There are releases for Microsoft Windows and Linux, and an unofficial build for macOS.First released in 2017, Basilisk is a perpetual beta intended to refine the UXP codebase it is built from. Pale Moon and other applications are also built from this codebase.Like Pale Moon, Basilisk is a fork of Firefox with substantial divergence. Basilisk has the user interface of the Firefox version 29–56 era (unlike Pale Moon, which has the Firefox 4–28 interface).

For add-ons, Basilisk has roughly similar support as Pale Moon for XUL/XPCOM extensions and NPAPI plugins, all of which are no longer supported in Firefox. Basilisk also had experimental support for current Firefox WebExtensions, but this was removed in February 2019.Unlike Pale Moon, Basilisk has limited support for Widevine DRM and WebRTC.

Firefox 2

Mozilla Firefox 2 is a version of Firefox, a web browser released on October 24, 2006 by the Mozilla Corporation.

Firefox 2 uses version 1.8 of the Gecko layout engine for displaying web pages. The release contained many new features not found in Firefox 1.5, including improved support for Scalable Vector Graphics (SVG) and JavaScript 1.7, as well as user interface changes.

On March 22, 2006, the first alpha version of Firefox 2 (Bon Echo Alpha 1) was released. It featured Gecko 1.8.1 for the first time. Mozilla Firefox 2.0.0.x is the final version officially supported on Windows NT 4.0, Windows 98 and Windows ME, although it can run on Windows 95 and Windows NT 3.51 using tweaks. Mac OS X 10.5 support was added October 18, 2007 with version

Firefox 2.0 featured updates to tabbed browsing environment, the extensions manager, the GUI, and the find, search, and software update engines; a new session restore feature; inline spell checking; and an anti-phishing feature which was implemented by Google as an extension, and later merged into the program itself.Mozilla ended support for Firefox 2 on December 18, 2008.

Firefox 3.0

Mozilla Firefox 3.0 is a version of the Firefox web browser released on June 17, 2008 by the Mozilla Corporation.Firefox 3.0 uses version 1.9 of the Gecko layout engine for displaying web pages. This version fixes many bugs, improves standards compliance, and implements many new web APIs compared to Firefox 2.0. Other new features include a redesigned download manager, a new "Places" system for storing bookmarks and history, and separate themes for different operating systems.

Firefox 3.0 had over 8 million unique downloads the day it was released, and by July 2008 held over 5.6% of the recorded usage share of web browsers. Estimates of Firefox 3.0's global market share as of February 2010 were generally in the range of 4–5%, and then dropped as users migrated to Firefox 3.5 and later Firefox 3.6.

Partially as a result of this, between mid-December 2009 and the end of January 2010, Firefox 3.5 was the most popular browser (when counting individual browser versions), passing Internet Explorer 7.Mozilla ended support for Firefox 3 on March 30, 2010 with the release of 3.0.19.

Firefox 4

Mozilla Firefox 4 is a version of the Firefox web browser, released on March 22, 2011. The first beta was made available on July 6, 2010; Release Candidate 2 (a base for the final version) was released on March 18, 2011. It was codenamed Tumucumaque, and was Firefox's last large release cycle. The Mozilla team planned smaller and quicker releases following other browser vendors. The primary goals for this version included improvements in performance, standards support, and user interface.There was one security update in April 2011 (4.0.1) and version 4 of the browser was made obsolete by the release of Firefox 5 in June 2011.This marked a transition to giving much less weight to major version numbers, with 5 more major version numbers used by December of that year (5, 6, 7, 8, and 9), compared to 4 in nearly a decade of Firefox development (1, 2, 3, 4).

Firefox OS

Firefox OS (project name: Boot to Gecko, also known as B2G) is a discontinued open-source operating system – made for smartphones, tablet computers and smart TVs – designed by Mozilla and external contributors. It is based on the rendering engine of the Firefox web browser, Gecko, and on the Linux kernel. It was first commercially released in 2013.

Firefox OS was designed to provide a complete, community-based alternative operating system, for running web applications directly or those installed from an application marketplace. The applications use open standards and approaches such as JavaScript and HTML5, a robust privilege model, and open web APIs that can communicate directly with hardware, e.g. cellphone hardware. As such, Mozilla with Firefox OS competed with commercially developed operating systems such as Apple's iOS, Google's Android, Microsoft's Windows Phone, BlackBerry's BlackBerry 10, Samsung's/Linux Foundation's Tizen and Jolla's Sailfish OS. In December 2015 Mozilla announced it would stop development of new Firefox OS smartphones, and in September 2016 announced the end of development. Successors to Firefox OS include the community-developed B2G OS (no longer maintained), Acadine Technologies' H5OS (now also discontinued), KaiOS Technologies' KaiOS and Panasonic's My Home Screen.

GNU IceCat

GNU IceCat, formerly known as GNU IceWeasel, is a free software rebranding of the Mozilla Firefox web browser distributed by the GNU Project. It is compatible with GNU/Linux, Windows, Android and macOS.The GNU Project attempts to keep IceCat in synchronization with upstream development of Firefox while removing all trademarked artwork. It also maintains a large list of free software plugins. In addition, it features a few security features not found in the mainline Firefox browser.

Gecko (software)

Gecko is a browser engine developed by Mozilla. It is used in the Firefox browser, the Thunderbird email client, and many other projects.

Gecko is designed to support open Internet standards, and is used by different applications to display web pages and, in some cases, an application's user interface itself (by rendering XUL). Gecko offers a rich programming API that makes it suitable for a wide variety of roles in Internet-enabled applications, such as web browsers, content presentation, and client/server.Gecko is written in C++ and JavaScript, and, since 2016, additionally in Rust. It is free and open-source software subject to the terms of the Mozilla Public License version 2. Mozilla officially supports its use on Android, Linux, macOS, and Windows.

History of Firefox

The history of the Firefox browser has its origins in an experimental branch of the Mozilla browser that was created by Dave Hyatt and Blake Ross. Beginning under the name Phoenix in September 2002, the browser was renamed Firebird in April 2003, and then Firefox in the following year. Firefox 1.0 was released on November 9, 2004, Firefox 1.5 on November 29, 2005, and Firefox 2.0 on October 24, 2006. The third major version of the browser, Firefox 3.0, was released on June 17, 2008, with Firefox 3.5 and Firefox 3.6 following on June 30, 2009, and January 21, 2010, respectively. Firefox 4 was released on March 22, 2011. Starting with version 5.0 in June 2011, a rapid-release cycle was put into effect, resulting in a new major-version release every six weeks. This schedule largely held until late 2016, when the release cycles became longer and more varied. As of 2019, major versions are being planned seven weeks apart.

Extended Support Release (ESR) versions of the browser became available starting in January 2012, with Firefox 10.0 ESR. Each ESR version was supported through nine rapid-release cycles for a total of 54 weeks. Updates to ESR versions of the browser were limited to security and stability fixes with no features being added or removed until the next ESR version. Initially scheduled for every seventh major version, the ESR release program continued with 17.0, 24.0, 31.0, 38.0 and 45.0. With Firefox 52.0 ESR, the release schedule for ESR versions changed to every eighth major version, with support extending to 76 weeks; under this scheme ESR versions continued with version 60.0, released on May 9, 2018.

As of April 18, 2019, the latest major version is Firefox 66, which was released on March 19, 2019.

The current supported official releases are Firefox 66.0.3 and Firefox 60.6.1 ESR.

Future development is continuing with Firefox 67.0 and onwards.

The next major ESR release will be Firefox 68.0 ESR.

List of web browsers

The following is a list of web browsers that are notable.


Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape. The Mozilla community uses, develops, spreads and supports Mozilla products, thereby promoting exclusively free software and open standards, with only minor exceptions. The community is supported institutionally by the not-for-profit Mozilla Foundation and its tax-paying subsidiary, the Mozilla Corporation.Mozilla's products include the Firefox web browser, Thunderbird e-mail client, Firefox OS mobile operating system, Bugzilla bug tracking system, Gecko layout engine, Pocket "read-it-later-online" service, and others.According to web browsers usage statistics, Mozilla's Firefox trails behind Google Chrome.

Mozilla Thunderbird

Mozilla Thunderbird is a free and open-source cross-platform email client, news client, RSS and chat client developed by the Mozilla Foundation. The project strategy was modeled after that of the Mozilla Firefox web browser. It is installed by default on Ubuntu desktop systems.

On December 7, 2004, version 1.0 was released, and received more than 500,000 downloads in its first three days of release, and 1,000,000 in 10 days.On July 6, 2012, Mozilla announced the company was dropping the priority of Thunderbird development because the continuous effort to extend Thunderbird's feature set was mostly fruitless. The new development model shifted to Mozilla offering only "Extended Support Releases", which deliver security and maintenance updates, while allowing the community to take over the development of new features.On December 1, 2015, Mozilla Executive Chair Mitchell Baker announced in a company-wide memo that Thunderbird development needs to be uncoupled from Firefox. She referred to Thunderbird developers spending large efforts responding to changes to Mozilla technologies, while Firefox was paying a tax to support Thunderbird development. She also said that she does not believe Thunderbird has the potential for "industry-wide impact" that Firefox does. At the same time, it was announced that Mozilla Foundation will provide at least a temporary legal and financial home for the Thunderbird project.

Mozilla software rebranded by Debian

In 2006, a branding issue developed when Mike Connor, representing the Mozilla Corporation, requested that the Debian Project comply with Mozilla standards for use of the Thunderbird trademark when redistributing the Thunderbird software. At issue were modifications not approved by the Mozilla Foundation, when the name for the software remained the same.

The Debian Project subsequently rebranded the Mozilla Firefox program, and other software released by Mozilla, so that Debian could distribute modified software without being bound by the trademark requirements that the Mozilla Foundation had invoked. The new names established by Debian were Iceweasel for Mozilla Firefox, Icedove for Mozilla Thunderbird, and Iceape for SeaMonkey. These changes were implemented in the subsequent version of Debian (Etch). In July 2007, Iceowl, a rebranded version of Mozilla Sunbird, was added to the unstable branch of Debian.In 2016, a number of Mozilla employees and Debian maintainers argued that the branding was no longer needed, and on 10 March 2016, Debian's unstable branch switched back to the Mozilla branding, with the stable branch planning to switch after Iceweasel's end of life.The decade-long branding issues between the Debian Project and Mozilla Corporation ended in 2017 when all software was de-branded back to their original names.

Netscape (web browser)

The Netscape web browser is the general name for a series of web browsers formerly produced by Netscape Communications Corporation, a former subsidiary of AOL. The original browser was once the dominant browser in terms of usage share, but as a result of the first browser war, it lost virtually all of its share to Internet Explorer.Netscape was discontinued and support for all Netscape browsers and client products was terminated on March 1, 2008.

Pale Moon (web browser)

Pale Moon is an open-source web browser with an emphasis on customizability; its motto is "Your browser, Your way". There are official releases for Microsoft Windows and Linux, an unofficial build for macOS, and contributed builds for various platforms.Pale Moon is a fork of Firefox with substantial divergence. The main differences are the user interface, add-on support, and running in single-process mode. Pale Moon retains the highly customizable user interface of the Firefox version 4–28 era. It also continues to support some types of add-ons that are no longer supported by Firefox.


Swiftfox was a web browser based on Mozilla Firefox. It was available for Linux platforms and distributed by Jason Halme. Swiftfox was a set of builds of Firefox optimized for different Intel and AMD microprocessors. Swiftfox was freely downloadable with open source code and proprietary binaries. Firefox extensions and plugins were compatible with Swiftfox, with notable exceptions. The name Swiftfox comes from the animal swift fox. Swiftfox differs from Firefox by a limited number of changes, and builds for different processors. Swiftfox was discontinued at some point prior to April 2017, and the project homepage now redirects to the creator's private Twitter account.


TenFourFox is a web browser for Power Macintosh computers, based on Mozilla's Gecko layout engine. It is a port of Mozilla Firefox for PowerPC-based Macintosh computers running Mac OS X to retain compatibility with the older architecture and older versions of the operating system, and to add PowerPC-specific optimizations for improved performance. The project was started after Mozilla announced that it would not release Firefox 4 for PowerPC versions of OS X. Like Firefox, it includes compatibility with a wide range of addons, Acid2 and Acid3 compliance, and HTML 5 and CSS 3 features; however, it also includes JavaScript just-in-time compilation, custom builds for specific PowerPC processor families, and AltiVec acceleration of key media codecs. The primary maintainer is Cameron Kaiser.

The project shares administration with Classilla, a fork of Mozilla Application Suite for Mac OS 9 and Mac OS 8.6.


Waterfox is an open-source web browser for x64 and ARM64 systems. It is intended to be speedy and ethical, and maintain support for legacy extensions dropped by Firefox, from which it is forked. There are official releases for Windows (including a portable version), macOS, Linux and Android.

Waterfox is based on Firefox and is compiled using various compilers and using Intel's Math Kernel Library, Streaming SIMD Extensions 3 and Advanced Vector Extensions. Linux builds are built with Clang. Waterfox is continuing to support the long-standing XUL and XPCOM add-on capability that Firefox removed in version 57.


XUL ( ZOOL), which stands for XML User Interface Language, is a user interface markup language developed by Mozilla. XUL is implemented as an XML dialect, enabling graphical user interfaces to be written in a similar manner to web pages. Such applications must be created using the Mozilla codebase (or a fork of it); the most prominent example is the Firefox web browser.

In the past, Firefox permitted add-ons to extensively alter its user interface via custom XUL code, but this capability was removed in Firefox 57 and replaced with the less-permissive WebExtensions API. (Three forks of Firefox still support the legacy capability: Pale Moon, Basilisk, Waterfox.)

Web apps or
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