Features of Mozilla Firefox

The features of Mozilla Firefox distinguish it from other web browsers such as Internet Explorer. It lacks many features found in other browsers, in an effort to combat interface bloat and to allow The Browser to be shipped as a small, pared-down core easily customizable to meet individual users' needs. Instead of Providing all features in the standard distribution, Firefox relies on the extension system to allow users to modify the browser according to their requirements.

Tabbed browsing

Firefox supports tabbed browsing, which allows users to open multiple pages in the same window. This feature was carried over from the Mozilla Application Suite, which in turn had borrowed the feature from the popular MultiZilla extension for Mozilla.

Firefox also permits the "homepage" to be a list of URLs delimited with vertical bars (|), which are automatically opened in separate tabs, rather than a single page.

Firefox 2 supports more tabbed browsing features, including a "tab overflow" solution that keeps the user's tabs easily accessible when they don't fit horizontally, "session store" which lets the user keep the opened tabs across the restarts, the "undo close tab" feature, etc.

Pop-up blocking

Firefox also includes integrated customizable pop-up blocking. Firefox was given this feature early in beta development, and it was a major comparative selling point of the browser until Internet Explorer gained the capability in the Windows XP Service Pack 2 beta. This blocks pop-ups from all web sites by default, but can be configured to allow individual sites to show pop-ups. It can also be turned off entirely to allow pop-ups from all sites. Firefox's pop-up blocking can be inconvenient at times — it prevents JavaScript-based links opening a new window while a page is loading unless the site is added to a "safe list" found in the options menu.

In many cases it is possible to view the pop-up's URL by clicking the dialogue that appears when one is blocked. This makes it easier to decide if the pop-up should be displayed.

Download manager

An integrated customizable download manager is also included. Downloads can be opened automatically depending on the file type, or saved directly to disk. By default, Firefox downloads all files to a user's desktop on Mac and Windows or to the user's home directory on Linux, but it can be configured to prompt for a specific download location. The download manager currently does not support cross-session resuming (stopping a download and resuming it after closing the browser).1 Another issue with the download manager is that it fails to close if small files or files already in the cache are downloaded. One advantage of the Firefox download manager is that the user can view the full source URL and destination path of the file being downloaded via the Properties box; Internet Explorer only shows the file name and source domain name.2

Live Bookmarks

Powered by RSS or Atom feeds, "Live Bookmarks", another feature of Firefox, allow users to dynamically monitor changes to their favorite news sources. When this feature was first introduced in version 1.0 PR, there were a few worries that Firefox was beginning to include non-essential features and that it was beginning to bloat the browser much like the Mozilla Suite. However, these worries have largely abated.

Instead of treating RSS-feeds as HTML pages like most news aggregators do, they are treated as bookmarks that are updated in real-time with a link to the appropriate source. Live bookmarks are updated automatically, however no browser option exists to prevent or control the automatic Live Bookmark updates.

Add-ons

There are 3 types of add-ons in Firefox: extensions (for additional browser functionality), themes (modified browser appearance), and plugins (to view additional web content). Firefox add-ons may be obtained from the official Mozilla Add-ons web site or from other sources.

Extensions

: See also: Firefox Extension system and List of Firefox extensions

Firefox users can add features and change functionality in Firefox by installing extensions. Extension functionality is varied; such as those enabling mouse gestures, those that block advertisements, and those that enhance tabbed browsing.

Features that the Firefox developers believed would be used by a small number of its users have not been included in Firefox and left to be implemented as extensions. Many Mozilla Suite features, such as IRC chat (ChatZilla) and calendar have been recreated as Firefox extensions. Extensions are also often a testing ground for features that are eventually returned to the main codebase. For example, MultiZilla was an extension that provided tabbed browsing when Mozilla lacked that feature.

While extensions provide a high level of customizability, PC World notes the difficulty a casual user would have in finding and installing extensions as compared to their features being available by default.

Most extensions are not created or supported by Mozilla. As extensions have the same rights to the user's system as Firefox itself, it's possible to create malicious extensions. Mozilla provides a repository of extensions that have been reviewed by volunteers to not contain malware. Since extensions are mostly created by third parties, they do not necessarily go through the same level of testing as official Mozilla products, and they may have bugs or vulnerabilities.

Themes

Firefox also supports a variety of themes/skins for changing its appearance. Themes are simply packages of CSS and image files. Many themes can be downloaded from the Mozilla Update web site.

The change of default theme from Qute to Winstripe in Firefox 0.9 was subject to vocal debate. The Winstripe theme was created by heavily modifying Pinstripe, a theme designed with Mac OS X in mind. Prior to that, Firefox and its predecessors had used the Qute theme, designed by Arvid Axelsson. Due to licensing issues, the theme was prevented from being released under the Mozilla Public License. Axelsson was upset about being notified about the theme change only a few days before it took place, and posted the transcript of his dialogue with Ben Goodger, who had informed him of the change, on the MozillaZine forums, breaking the news before it was formally announced. Although many people criticized the new theme when it was rolled out, eventually the tension subsided. Axelsson continues to produce Qute privately. Axelsson still makes Mozilla Thunderbird's default theme.

Dictionaries

Another type of XPI add‐ons for Firefox — dictionaries for spell checking of input fields.

Plugins

Firefox supports plugins based on Netscape Plugin Application Program Interface (NPAPI), i.e. Netscape-style plugins. As a side note, Opera and Internet Explorer 3.0 to 5.0 also support NPAPI.

On June 30, 2004, the Mozilla Foundation, in partnership with Adobe, Apple, Macromedia, Opera, and Sun Microsystems, announced a series of changes to web browser plugins. The new API will allow web developers to offer richer web browsing experiences, helping to maintain innovation and standards. The new plugin technologies are expected to be implemented in the future versions of the Mozilla applications.

Mozilla Firefox 1.5 and later versions include the Java Embedding plugin, which allow Mac OS X users to run Java applets with the latest 1.4 and 5.0 versions of Java (the default Java software shipped by Apple is not compatible with any browser, except its own Safari).

Customizability

Beyond the use of Add-ons, Firefox additional customization features.

The position of the toolbars and interface are customizable
Hidden preferences in about:config which can be used to modify the behaviour of features and tweak performance.
User stylesheets to change the style of webpages and Firefox's UI.

Web technologies support

Firefox has extensive support for most basic Web standards including HTML, XML, XHTML, CSS, JavaScript, DOM, MathML, SVG, XSL and XPath. Firefox's standards support and growing popularity have been credited as one reason Internet Explorer 7 was to be released with improved standards support.

Since Web standards are often in contradiction with Internet Explorer's behavior, Firefox, like other browsers, has a quirks mode. This mode attempts to mimic Internet Explorer's quirks mode, but it isn't completely compatible. Because of the differing rendering, PC World notes that a minority of pages do not work in Firefox.

c|Net notes that Firefox does not support ActiveX controls by default, which can also cause webpages to be missing features or to not work at all in Firefox. Mozilla made the decision to not support ActiveX due to potential security vulnerabilities, its proprietary nature and its lack of cross-platform compatibility. There are methods of using ActiveX in Firefox such as via third party plugins but they do not work in all versions of Firefox or on all platforms.

Beginning on December 8, 2006, Firefox trunk nightly builds pass the Acid2 CSS standards compliance test, so all future releases of Firefox 3 will pass the test.

Cross-platform support

Mozilla Firefox runs on a wide variety of platforms. Releases available on the primary distribution site support the following operating systems:

Various versions of Microsoft Windows, including 98, 98SE, Me, NT 4.0, 2000, XP, Server 2003 and Vista
Mac OS X
Linux-based operating systems using X.Org Server or XFree86

Builds for Solaris (x86 and SPARC), contributed by the Sun Beijing Desktop Team, are available on the Mozilla web site.

Mozilla Firefox installation on Windows 95 requires a few additional steps.

Since the source code is available, it can also be compiled and run on a variety of other architectures and operating systems. Thus, Firefox is also available for many other systems. This includes OS/2, AIX, and FreeBSD. Builds for Windows XP Professional x64 Edition are also available. Mozilla Firefox is also the browser of choice for a good number of smaller operating systems, such as SkyOS and ZETA.

Firefox uses the same profile format on the different platforms, so a profile may be used on multiple platforms, if all of the platforms can access the same profile; this includes, for example, profiles stored on an NTFS (via FUSE) or FAT32 partition accessible from both Windows and Linux, or on a USB flash drive. This is useful for users who dual-boot their machines. However, it may cause a few problems, especially with extensions.

Security

Firefox includes many features designed to improve security. Key features include a sandbox security model, same origin policy, external protocol whitelisting, a phishing detector (in Firefox 2.0), Clear Private Data, and master passwords.

Firefox is open source software, and thus, its source code is visible to everyone. This allows anyone to review the code for security vulnerabilities, whether their intentions are good or malicious. It also allowed the U.S. Department of Homeland Security to give funding for the automated tool Coverity to be run against Firefox code.

Additionally, Mozilla has a security bug bounty system - anyone who reports a valid critical security bug receives a $500 (US) cash reward for each report and a Mozilla T-shirt.

Vulnerability statistics

As of December 2007, the security firm Secunia reports 4 of 18 security flaws not yet fixed for Mozilla Firefox, as opposed to 7 of 20 security flaws not yet fixed for Microsoft Internet Explorer. In addition, according to Secunia, Firefox's vulnerabilities tend to be less critical than Internet Explorer's. While Internet Explorer users who have installed Windows XP Service Pack 2 are only affected by those 3 vulnerabilities, users of older versions of Windows are potentially affected by the 21 vulnerabilities in Internet Explorer 6 as Service Pack 2 is only available for Windows XP.

On the whole, Firefox security vulnerabilities have been patched relatively quickly. Symantec's Internet Security Threat Report Vol. 10, based on data from the first half of 2006, reported that while Firefox had more vulnerabilities than Internet Explorer during that time period (47 vs. 38), Firefox's vulnerabilities were fixed on average one day after the exploit code was made available, as compared to nine days for Internet Explorer.

Some experts have speculated that as Firefox becomes more popular, more vulnerabilities will be found, a claim that Mitchell Baker, president of the Mozilla Foundation, has denied.

Expert and media coverage

The United States Computer Emergency Readiness Team (US-CERT) stated that Internet Explorer's design makes it very difficult to secure. In contrast, almost none of their concerns apply to Firefox.

Some security experts, including Bruce Schneier and David A. Wheeler, recommended that users should stop using Internet Explorer for normal browsing, and switch to a different browser instead; Wheeler specifically recommended Firefox.

Several technology columnists have suggested the same, including Wall Street Journal columnist Walter S. Mossberg, Washington Post columnist Rob Pegoraro, USA Today’s Byron Acohido and Jon Swartz, Forbes's Arik Hesseldahl, eWEEK.com Senior Editor Steven J. Vaughan-Nichols, and Desktop Pipeline’s Scot Finnie.

Usability

Firefox was designed for the average user, hiding advanced configuration and making features that do not require user interaction to function. Jim Repoza of eWEEK states Firefox also won UK Usability Professionals' Association's 2005 award for "Best software application".

Microsummaries

Support for Microsummaries was added in version 2.0. Microsummaries are short summaries of web pages that are used to convey more information than page titles. Microsummaries are regularly updated to reflect content changes in web pages so that viewers of the web page will want to revisit the web page after updates. Microsummaries can either be provided by the page, or be generated by the processing of an XSLT stylesheet against the page. In the latter case, the XSLT stylesheet and the page that the microsummary applies to are provided by a microsummary generator.

External links

Other features

Screenshot of performing "Find as you type". "ency" was being typed and the first matched text was highlighted in green.

Firefox also has an incremental find feature known as find as you type, invoked by the slash (/) key. With this feature enabled, a user can simply begin typing a word while viewing a web page, and Firefox automatically searches for it and highlights the first instance found. As the user types more of the word, Firefox refines its search. Also, if the user's exact query does not appear anywhere on the page, the "Find" box turns red.

There is also a built-in Mycroft Web search function with extensible search engine listing; by default, Firefox includes plugins for Google and Yahoo!, and also includes plugins for looking up a word on dictionary.com and browsing through Amazon.com listings. Other popular Mycroft search engines include Wikipedia, eBay, and IMDb.

Smart keywords can be used to quickly search for information on specific Web sites. A smart keyword is user-defined to be associated with a search box on a given site, and then can be used in the Firefox location bar as a shortcut to search that site. For example, "imdb" is a pre-defined smart keyword; to search for information about the movie 'Firefox' on IMDb, jump to the location bar with the CTRL+L shortcut, type "imdb Firefox" and press the Enter key.

It should be noted that most of the aforementioned features are not unique to Firefox.