Firefox

History

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. The community-driven SeaMonkey was formed and eventually replaced the Mozilla Application Suite in 2005.

The Firefox project has undergone several name changes. 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. 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. The name Firefox was said to be derived from a nickname of the red panda, 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.

The Firefox project went through many versions before the version 1.0 was released on November 9, 2004.

Features

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 Yahoo! Search, which is a front end of Microsoft search engine Bing, by default in most localizations. 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 is scheduled to be removed in September 2016.

Functions can be added through add-ons created by third-party developers. Add-ons are primarily implemented by means of the XUL and XPCOM APIs, which allow them to directly access and manipulate much of the browser's internal functionality. On August 21, 2015, Firefox developers announced that due to planned changes to Firefox's internal operations, including the planned implementation of a new multi-process architecture codenamed "Electrolysis" ("E10s", introduced to some users in version 48), Firefox adopted a new extension architecture known as WebExtensions, available to desktop version and Firefox for Android (considered stable in version 48). WebExtensions uses HTML and JavaScript APIs and is designed to be similar to the Google Chrome and Microsoft Edge extension systems, and run within a multi-process environment, but does not enable the same level of access to the browser. Solutions will be available to allow older add-ons to operate within the new architecture, but by 2017, XPCOM and XUL add-ons will no longer be supported.

Firefox can have themes added to it, so users can experience Firefox in a more personal way. There are websites where users can create and download personalized themes, with their choice of colors and images. This can make the experience of using Firefox more fun compared to other web browsers that do not offer custom-built themes. However, Mozilla has announced its intention to discontinue Firefox themes. The Firefox add-on website also gives users the ability to add other applications such as games, ad-blockers, screenshot apps, and many other useful apps.

Standards

Firefox implements many web standards, including HTML4 (almost full HTML5), XML, XHTML, MathML, SVG 2 (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. 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. 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.

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, "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

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

Security

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

The Mozilla Foundation offers a "bug bounty" (US$3000 to US$7500 cash reward) 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 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 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.

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

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," she said.

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. 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 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.

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.

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.

Beginning with Firefox 44 (2016), 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.

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. 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.

As of 2016, Firefox is 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. Version 50 includes a limited sandbox that isolates the content rendering process (separated thanks to the Electrolysis project), which will be progressively enhanced to improve security.

Localizations

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. As of March 2017, currently supported 52.0, 52.0esr, and 45.8.0esr are available in 89 locales (79 languages).

Platform availability

The desktop version of Firefox is available and supported for Windows, macOS and Linux, while Firefox for Android is available for Android (formerly Firefox for mobile, it also ran on Firefox OS). In September 2013, the Windows 8 Touch interface, optimized for touchscreen use, was introduced on the "Aurora" release channel; however, the project has since been cancelled as of March 2014, citing a lack of user adoption of the beta versions.

OS support history

Unofficial ports

Firefox has also been ported to FreeBSD, NetBSD, OpenBSD, OpenIndiana, OS/2 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.

Firefox on Unix

Firefox is also ported to Solaris and OpenSolaris by Oracle Solaris Desktop Beijing Team, unofficial port of Firefox 3.6.x to IBM AIX and unofficial port of v1.7.x to UnixWare.

Firefox 3.5.9 is the last version to work on HP-UX 11i, as packaged by Hewlett-Packard.

x86 family

Native 64-bit builds are officially supported on Linux, macOS, and Windows (since version 42).

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.

The official releases of Firefox for macOS 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.

The 32-bit and 64-bit versions of Windows can be used to run 32-bit Firefox. In late 2012, Mozilla announced 64-bit Windows builds would be stopped but later reversed the decision. As of April 2015, 64-bit Windows builds are available as 38.0 Beta and newer. 64-bit builds for Windows are officially supported as of November 2015 with the release of Firefox 42. All NPAPI plugins except Adobe Flash Player are blacklisted and unsupported on both 32 and 64-bit versions.

Other CPU architectures

Besides x86, Firefox also supports other CPU architectures including ARMv7, SPARC, PowerPC, and 68k on different tiers.

System requirements

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

Firefox for Android

Firefox for Android, code-named 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. On March 29, 2011, besides Maemo, Version 4 was added for Android. 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. 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.

Firefox for iOS

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. Apple later opened their "Nitro" JavaScript engine to third-party browsers. 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.

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), and "Nightly". As of November 25, 2016, Firefox 51 is in the "Beta" channel, Firefox 52 is in the "Developer Edition" channel, and Firefox 53 is in the "Nightly" channel.

Extended Support Release

Firefox Extended Support Release, abbreviated to ESR, 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. 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.

Licensing

Firefox source code is free software, with most of it being released under the Mozilla Public License (MPL) version 2.0. 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, 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. 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. 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 (and Socorro server).

Trademark and logo

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.

There has been some controversy over the Mozilla Foundation's intentions in stopping certain open source distributions from using the "Firefox" trademark. Open source browsers "enable greater choice and innovation in the market rather than aiming for mass-market domination." 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 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. 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.

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.

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. 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 usually 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 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 software distributors who distribute modified versions of Firefox do not use the icon.

Promotion

Firefox was adopted rapidly, with 100 million downloads in its first year of availability. 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".

Firefox continued to heavily market itself by releasing a marketing portal dubbed "Spread Firefox" (SFX) on September 12, 2004, 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.” A two-page ad in the December 16th 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. 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."

In celebration of the third anniversary of the founding of the Mozilla Foundation, the "World Firefox Day" campaign was established on July 15, 2006, 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.

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. After Firefox reached 500 million downloads on February 21, 2008, the Firefox community celebrated by visiting Freerice to earn 500 million grains of rice.

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

Performance

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 each of 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 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.

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.

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.

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.

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.

Market adoption

Downloads have continued at an increasing rate since Firefox 1.0 was released in November 2004, and as of July 31, 2009 Firefox had already 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, IBM asked all employees (about 400,000) 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 February 2016, Firefox was the second most widely used "desktop browser" (and that position makes it the third most popular with approximately 10% of worldwide usage share of web browsers across all platforms).