Mozilla Firefox
Firefox Logo, 2017.svg
Customized Firefox 57 (Quantum) running on Windows 10
Customized Firefox 57 (Quantum) running on Windows 10
Initial releaseSeptember 23, 2002; 16 years ago (2002-09-23)
Stable release(s)
Standard67.0 / May 21, 2019; 1 day ago (2019-05-21)[1]
Extended Support Release60.7.0 / May 21, 2019; 1 day ago (2019-05-21)[2]
Preview release(s)
Beta & Developer Edition68.0beta / May 21, 2019; 1 day ago (2019-05-21)[3][4]
Nightly69.0a1 / May 20, 2019; 2 days ago (2019-05-20)[5][6] Edit this at Wikidata
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]

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 March 2019, Firefox has 9.57% 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]


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.

Screenshot of Phoenix 0.1 on Windows XP

The Firefox project has undergone several name changes.[41][42][43][44][45][46][47][48] The nascent browser was originally named Phoenix, after the mythical bird that rose triumphantly from the ashes of its dead predecessor (in this case, from the "ashes" of Netscape Navigator, after was sidelined by Microsoft Internet Explorer in the "First Browser War"). Phoenix was renamed due to a trademark claim from Phoenix Technologies. The replacement name, Firebird, provoked an intense response from the Firebird database software project.[49][50] The Mozilla Foundation reassured them that the browser would always bear the name Mozilla Firebird to avoid confusion. After further pressure, Mozilla Firebird became Mozilla Firefox on February 9, 2004.[51] The name Firefox was said to be derived from a nickname of the red panda,[52] which became the mascot for the newly named project.[53]

The Firefox project went through many versions before version 1.0 was released on November 9, 2004.[54] For the abbreviation of Firefox, Mozilla prefers Fx or fx, though it is often abbreviated as FF.[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]

On May 3, 2019, the expiration of an intermediate signing certificate caused Firefox to automatically disable all browser extensions (add-ons).[59][60] Mozilla began roll-out of a fix shortly thereafter, using their Mozilla Studies component.[59][60]

Other Languages
Afrikaans: Mozilla Firefox
Alemannisch: Mozilla Firefox
العربية: فايرفوكس
aragonés: Mozilla Firefox
asturianu: Mozilla Firefox
Avañe'ẽ: Aguaratata
azərbaycanca: Mozilla Firefox
Bân-lâm-gú: Mozilla Firefox
беларуская: Mozilla Firefox
беларуская (тарашкевіца)‎: Mozilla Firefox
български: Mozilla Firefox
bosanski: Firefox
brezhoneg: Mozilla Firefox
català: Firefox
Чӑвашла: Mozilla Firefox
čeština: Mozilla Firefox
dolnoserbski: Mozilla Firefox
Ελληνικά: Mozilla Firefox
español: Mozilla Firefox
Esperanto: Mozilla Firefox
فارسی: فایرفاکس
føroyskt: Mozilla Firefox
français: Mozilla Firefox
Gàidhlig: Firefox
հայերեն: Mozilla Firefox
Արեւմտահայերէն: Մոզիլլա Ֆայրֆոքս
hornjoserbsce: Mozilla Firefox
hrvatski: Mozilla Firefox
Bahasa Indonesia: Mozilla Firefox
interlingua: Mozilla Firefox
Ирон: Mozilla Firefox
íslenska: Mozilla Firefox
italiano: Mozilla Firefox
ქართული: Mozilla Firefox
kaszëbsczi: Mozilla Firefox
қазақша: Mozilla Firefox
Kiswahili: Mozilla Firefox
Кыргызча: Mozilla Firefox
latviešu: Mozilla Firefox
Lëtzebuergesch: Mozilla Firefox
lietuvių: Firefox
lingála: Firefox
lumbaart: Mozilla Firefox
македонски: Mozilla Firefox
Malagasy: Mozilla Firefox
Bahasa Melayu: Mozilla Firefox
မြန်မာဘာသာ: Firefox
Nederlands: Mozilla Firefox
日本語: Mozilla Firefox
norsk nynorsk: Mozilla Firefox
Oromoo: Firefox
oʻzbekcha/ўзбекча: Mozilla Firefox
ਪੰਜਾਬੀ: ਫ਼ਾਇਰਫ਼ੌਕਸ
پنجابی: فائرفاکس
polski: Firefox
português: Mozilla Firefox
română: Mozilla Firefox
русский: Mozilla Firefox
Scots: Firefox
sicilianu: Mozilla Firefox
Simple English: Mozilla Firefox
slovenčina: Mozilla Firefox
slovenščina: Mozilla Firefox
Soomaaliga: Firefox
کوردی: فایەرفۆکس
српски / srpski: Мозила фајерфокс
srpskohrvatski / српскохрватски: Mozilla Firefox
Basa Sunda: Mozilla Firefox
Taqbaylit: Firefox
татарча/tatarça: Mozilla Firefox
тоҷикӣ: Mozilla Firefox
Türkçe: Mozilla Firefox
українська: Mozilla Firefox
vepsän kel’: Mozilla Firefox
Tiếng Việt: Mozilla Firefox
吴语: Firefox
ייִדיש: Mozilla Firefox
žemaitėška: Mozilla Firefox
中文: Firefox