Using Firefox/Extensions

Extensions are small add-ons that add new functionality to Firefox, but should not be confused with plug-ins.

In Firefox, add-ons is a general term that in Firefox is applied to extensions proper, themes, userscripts, userstyles, service workers, plug-ins, spellcheckers and language packs. Extensions rely on built-in frameworks and API s within Firefox, and are integrated into the browser after installation. Whereas plug-ins, such as Adobe Flash, use programming not native to Firefox, and are usually embedded into a web page only when said page contains code that requires Flash to be loaded.

Extensions that use the legacy XPCOM, XUL, and JetPack frameworks, are supported until Firefox 56.0. These are known both as legacy extensions, and legacy versions of Firefox, respectively. In late 2018, Mozilla ceased support for XUL-based extensions, and no longer hosts them, though various ways of obtaining legacy extensions still exist.

WebExtensions were initially supported in Firefox 48.0, and beginning with Firefox 57.0, only WebExtensions are supported.

What can extensions do
Extensions can add anything from a toolbar button to a completely new feature. They allow the browser to be customized to fit the personal needs of each user, if they need additional features, while Firefox proper remains relatively unadorned.

Many links herein will not necessarily point to a specific extension, but rather to general links at the Mozilla Addons.

Mozilla Addons
Most extensions for Firefox, SeaMonkey, Thunderbird, and derivatives are available at the Mozilla Addons site, which hosts well over a thousand extensions. The great number of addons may make it difficult for people to find what they want.

Mozilla Addons has easy-to-use pages linking to extensions by category, popularity, or recommended status.

There are many themes available, which make Firefox more attractive. The most popular themes are listed here.

Mozilla once launched Fashion Your Firefox, an easy-to-use service for users who didn't want to go through the entire library of addons to choose just a few good ones based on what they use Firefox for. Fashion Your Firefox has since long been discontinued.

The below sections herein provide links to specific extension categories at Mozilla Addons — this means that the information will stay up-to-date.

Alternative sources
Since Mozilla no longer hosts legacy extensions, then their installers in the form of XPI files are still available from a number of places:
 * back-ups by various open-source volunteers;
 * occasional mirrors of Mozilla Addons FTP site;
 * the developers' own websites, or original web resources (MozDev, GitHub); and
 * at the Internet Archive WayBack Machine.

The Internet Archive serves as the resource closest-possible to the original Mozilla Addons site, and hosts most extensions' description and version pages. If an extension page was archived before October/November 2018 (inclusive), then it's mostly functional, too, such as showing if an extension is compatible with the visiting browser.

The requirement to see an extension's archived pages is to know its original address at the Mozilla Addons site. This can be found out from an extant extension's install information in a browser, or by searching the Internet using the addon's name.

If the "Add to Firefox" button on the archived page of an extension, or in its versions page is active (usually coloured green), then clicking the button may redirect the user to the extension's installer (XPI) file, but not always. The workaround is to right-click on the "Add to Firefox" button, and open the button's link (that directs to an XPI file) in a new tab. This would lead to a couple of redirects to the correct XPI file. Note also, that you'll have to allow installation of extensions from web.archive.org in an extension install notification window.

Not all extension installers are available from the WayBack Machine, due to not having been archived when they were originally available.

Alternative, and in some cases, more technical download sources of extensions for Firefox are available at XULRunner Hall of Fame at MozDev, at mirror.umd.edu, and at http://ftp.metu.edu.tr.

Content blocking

 * Adblock Plus &mdash; Blocks or hides advertisements and other annoyances from web pages, while still retaining the correct page format. It is designed around blocklists, and allows you to block flash and image banners built into the web page, as well as scripts. You add your own filters using wildcards (*) for simple custom filters, or regular expressions for advanced ones. Adblock Plus automatically downloads a pre-set blocklist, and provides additional lists of blocklists to enable and download, based on region or function (such as cryptominers).


 * Flashblock &mdash; A legacy Firefox add-on to easily block Flash, Silverlight, and HTML5 animations. The initial Flash file in each embed does get downloaded, but its animations are replaced with a click-to-play icon. Additional downloads via Flash are won't be initialised either.

Download Tools

 * DownThemAll! &mdash; Easily manage downloads while accelerating them as well.
 * Video DownloadHelper &mdash; Download video and audio files &mdash; Flash Video (.flv) files from sites like YouTube, MP3 files, and more.

E-mail and social

 * Cookiepie &mdash; An extension to handle multiple web accounts simultaneously, opening many Gmail, Yahoo, Hotmail accounts in different tabs on the same browser. This extension is currently unmaintained.


 * All the below links are very outdated, with the last update made on 14 July 2013, which makes the newest links nearly seven years old as of January 2020. They are displayed here for historical purposes.


 * StumbleUpon &mdash; Lets you 'stumble upon' websites that have been recommended ("thumbed up") by friends and community members with interests similar to your own. See also StumbleUpon website.

Themes

 * Vista-aero &mdash; A theme for Firefox meant to look like Internet Explorer 7 in Windows Vista, with Aero-like visual effects.

Miscellaneous

 * BBCode &mdash; Enables you to quickly and easily insert various BBCode tags in editable textboxes from the context menu. Very handy for customizing posts on forums.


 * ChatZilla &mdash; A simple, straightforward Internet Relay Chat (IRC) client.


 * FoxyTunes &mdash; Adds media player controls within Firefox. Currently supports many different music players across multiple platforms.


 * FasterFox &mdash; A simple-to-use performance and network tweaker. Fasterfox allows you to change certain setting to make Firefox load pages more quickly, depending on your computer speed and Internet connection.


 * Wikipedia &mdash; Provides text formatting options in the context menu for use on wiki sites based on Mediawiki, such as Wikipedia and Wikibooks.

Mouse gestures

 * All-in-one mouse gestures &mdash; Enables you to use the mouse for a wide variety of customizable shortcuts.

Navigation

 * Linkification &mdash; Injects CSS on the fly making text URLs clickable with the default option to suppress referrer information.


 * Paste &amp; Go &mdash; Lets you paste a URL from the clipboard and directly load it.

News

 * Sage &mdash; A lightweight RSS and Atom feed aggregator. Very useful for viewing news from many sites.

Page Display

 * Image Zoom &mdash; Adds zoom functionality for images. Functionality is also included in the Mouse Gestures extension.

Personal information management

 * Calculator &mdash; A simple calculator extension.


 * Calculator &mdash; An advanced calculator extension.


 * Calendar &mdash; An iCal compatible Calendar for Firefox. You can download calendars for your favourite sports teams, etc., from iCal Share


 * Quick Note &mdash; A note taking extension with advanced features.

Search tools

 * termBlaster &mdash; Lets you search selected text using search engines selected by context menu. It comes with 110+ search engines from encyclopedias to translators to web-search engines organized in folders.


 * Dictionary Search &mdash; Looks up selected word in a (customizable) online dictionary. Functionality is also included in the SmartSearch extension, which lacks the 4 search limitation.


 * Googlebar &mdash; The Google Toolbar for Firefox. Additionally, Googlebar Lite provides a simpler interface (which is recommended for new users).


 * Groowe Search Toolbar &mdash; Groowe Search Toolbar bundles Google toolbar, Yahoo, Ask Jeeves, Teoma, Amazon, Download.com and others. The application is available for Internet Explorer as well.

Tabs and windows

 * Focus Last Selected Tab &mdash; Brings focus to the last selected tab when closing the active tab. Functionality is also included in the TabMix extension.


 * Session Saver &mdash; Saves the open tabs when closing the browser, and restores them upon restarting it. Functionality is also included in the TabMix extension.


 * Single Window &mdash; A simple extension that allows Mozilla to fully utilize the built-in tabbed browsing behavior. Traps links that would normally open in a new window. Functionality is also included in the TabMix extension.


 * Tabbrowser Preferences &mdash; Enables enhanced control for tabbed browsing. Most functionality is also included in the TabMix extension. Recommended for users who would like to change the way tabs behave in Firefox.


 * TabMixPlus An extension that allows considerable customisation in the use of tabs and windows as well as a "restore" function that is as useful (or better) then the built in FireFox one.


 * Undoclosetab &mdash; Reopen a closed tab. Functionality is also included in the TabMix, SessionSaver, and Mouse Gestures extensions.