View source for Add-on (Mozilla)

{{Short description|Software modules to extend Firefox web browsers}}
{{Firefox TOC}}
'''Add-on''' is the [[Mozilla]] term for [[software]] modules that can be added to the [[Firefox]] [[web browser]] and related [[application software|applications]]. Mozilla hosts them on its official add-on [[website]].<ref name="official-site">{{cite web |title=Official Add-on website |url=https://addons.mozilla.org/ |access-date=10 February 2019 |publisher=Mozilla}}</ref>

[[Browser extension]]s are the primary type of add-on. In 2017, Mozilla enacted major changes to the [[application programming interface]] (API) for extensions in Firefox, replacing the long-standing [[XUL]] and [[XPCOM]] APIs with the [[WebExtensions API]] that is modeled after [[Google Chrome]]'s API.<ref>{{Cite web|url=https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-ons/|title=The Future of Developing Firefox Add-ons|website=Mozilla Add-ons Blog|date=21 August 2015 |language=en-US|access-date=2018-12-15}}</ref><ref name="57plan">{{Cite web|url=https://blog.mozilla.org/addons/2017/08/10/upcoming-changes-compatibility/|title=Upcoming Changes in Compatibility Features|website=Mozilla Add-ons Blog|date=10 August 2017 |language=en-US|access-date=2018-12-15}}</ref><ref name="legacy">{{Cite web|url=https://www.ghacks.net/2017/08/12/how-to-enable-legacy-extensions-in-firefox-57/|title=How to enable legacy extensions in Firefox 57 - gHacks Tech News|website=www.ghacks.net|date=12 August 2017 |access-date=2018-12-14}}</ref> Thus add-ons that remain compatible with Firefox are now largely compatible with Chrome as well.<ref>{{cite web |title=Porting a Google Chrome extension |url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Porting_a_Google_Chrome_extension |publisher=Mozilla |access-date=30 December 2018}}</ref> As of January, 2024, there are more than 36,000 add-ons and over 495,000 themes available for Firefox.<ref>{{cite web |title=Search results (Extensions) – Add-ons for Firefox (en-US) |url=https://addons.mozilla.org/en-US/firefox/search/?type=extension |website=addons.mozilla.org |publisher=Mozilla |access-date=28 January 2024}}</ref><ref>{{cite web |title=Search results (Themes) – Add-ons for Firefox (en-US) |url=https://addons.mozilla.org/en-US/firefox/search/?type=statictheme |website=addons.mozilla.org |publisher=Mozilla |access-date=28 January 2024}}</ref>

==Current add-ons==

===Extensions===

====WebExtensions====
Starting with Firefox 57, only the new [[WebExtensions API]] is supported.<ref name="57plan"/><ref>{{cite web |title=Browser extensions |url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions |website=MDN |publisher=Mozilla |access-date=10 February 2019}}</ref>

===Themes===
Early versions of Firefox supported [[Theme (computing)|themes]] that could greatly change the appearance of the browser, but this was scaled back over time. Current themes are limited to changing the background and text color of toolbars.<ref>{{cite web |title=Themes for Firefox |url=https://addons.mozilla.org/en-US/firefox/themes/}}</ref> (These lightweight themes were formerly called personas.<ref>{{cite web |title=Personas are now Firefox Themes |url=https://blog.mozilla.org/addons/personas-are-now-firefox-themes/}}</ref>)

==Historical add-ons==

=== Extensions ===

==== Legacy extensions ====
Prior to 2017, [[Firefox]] supported [[browser extension|extensions]] developed with different APIs: [[XUL]], [[XPCOM]], and [[Mozilla Jetpack|Jetpack]].<ref>[https://developer.mozilla.org/en-US/Add-ons/Overlay_Extensions/Firefox_addons_developer_guide/Technologies_used_in_developing_extensions Chapter 2: Technologies used in developing extensions - Firefox addons developer guide | MDN] {{Webarchive|url=https://web.archive.org/web/20161005134018/https://developer.mozilla.org/en-US/Add-ons/Overlay_Extensions/Firefox_addons_developer_guide/Technologies_used_in_developing_extensions |date=2016-10-05 }}. Developer.mozilla.org. Retrieved on 2013-07-21.</ref> [[Mozilla]] now refers to these as legacy extensions.<ref name="legacy"/>

=== Plug-ins ===
[[Plug-in (computing)|Plug-ins]] are no longer supported in Firefox. In the past, they were used to handle [[media type]]s for which the application did not have built-in capability. They were [[deprecation|deprecated]] due to security concerns and improvements in [[Web API]]s.<ref>{{cite web | first=Benjamin | last=Smedberg | url=https://blog.mozilla.org/futurereleases/2015/10/08/npapi-plugins-in-firefox/ | title=NPAPI Plugins in Firefox | work=Future Releases | publisher=[[Mozilla Foundation]] | date=8 October 2015}}</ref> The last one that was officially supported was [[Adobe Flash Player]], which Adobe discontinued in 2020.<ref>{{cite web|url=https://techcrunch.com/2017/07/25/get-ready-to-say-goodbye-to-flash-in-2020/|title=Get ready to finally say goodbye to Flash — in 2020|last=Lardinois|first=Frederic|work=TechCrunch|date=25 July 2017 |access-date=2017-07-25}}</ref><ref>{{cite web |title=End of support for Adobe Flash |url=https://support.mozilla.org/en-US/kb/end-support-adobe-flash |publisher=Mozilla |access-date=9 April 2021}}</ref>

==Restrictions==
[[Mozilla]] had no mechanism to restrict the privileges of legacy [[Firefox]] extensions. This meant that a legacy extension could read or modify the data used by another extension or any file accessible to the user running Mozilla applications.<ref>{{cite web|url=http://www.intelligentexploit.com/articles/Abusing,-Exploiting-and-Pwning-with-Firefox-Add-ons.pdf|title=Abusing, Exploiting and Pwning with Firefox Add-ons|access-date=2013-10-23|archive-url=https://web.archive.org/web/20160305163019/http://www.intelligentexploit.com/articles/Abusing,-Exploiting-and-Pwning-with-Firefox-Add-ons.pdf|archive-date=2016-03-05|url-status=dead}}</ref> But the current WebExtensions API imposes many restrictions.<ref>{{cite web |title=Security Best Practices |url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Security_best_practices |website=MDN |publisher=Mozilla |access-date=10 February 2019}}</ref>

Starting with Firefox 40, Mozilla began to roll out a requirement for extension signing.<ref>{{cite web|last1=Fisher|first1=Dennis|title=Firefox 40 Begins Warning Users About Unsigned Add-Ons|url=https://threatpost.com/firefox-40-begins-warning-users-about-unsigned-add-ons/114237|website=Threatpost|date=12 August 2015 |access-date=20 August 2015}}</ref> It is now required in all official Firefox releases.<ref>{{cite web|title=Extension Signing|url=https://wiki.mozilla.org/Add-ons/Extension_Signing|website=Mozilla.org Wiki|publisher=Mozilla|access-date=20 August 2015}}</ref>

==Website==
{{Infobox website
| name = Add-ons for Firefox
| logo = Firefox Browser Add-ons logo.svg
| url = {{URL|https://addons.mozilla.org}}
| commercial = No
| type = Hosts add-ons
| language = 
| registration = Free; only needed for developers or for special features
| owner = [[Mozilla Foundation]]
| launch_date = 
| current_status = Active
}}
The [[Mozilla]] add-ons website is the official repository for [[Firefox]] add-ons.<ref name="official-site"/> In contrast to [[mozdev.org]] which provides free hosting for Mozilla-related projects, the add-ons site is tailored for [[user (computing)|users]]. By default, Firefox automatically checks the site for updates to installed add-ons.<ref>{{Cite web|url=https://developer.mozilla.org/en-US/Add-ons/Updates|title=Updates|website=Mozilla Developer Network|language=en-US|access-date=2017-10-28}}</ref>

In January 2008, Mozilla announced that the site had accumulated a total of 600 million add-on downloads and that over 100 million installed add-ons automatically check the site for updates every day.<ref>{{Cite web
 |url= http://blog.mozilla.com/metrics/2008/01/30/600000000-add-on-downloads/
 |work=Blog of Metrics
 |publisher=Mozilla Foundation
 |title=600,000,000 Add-on Downloads
 |date=30 January 2008
 |first=Justin
 |last=Scott
}}</ref> In July 2012, the total had increased to 3 billion downloads from the site.<ref>{{cite web|title=Firefox Add-ons Cross More Than 3 Billion Downloads!|url=https://blog.mozilla.org/blog/2012/07/26/firefox-add-ons-cross-more-than-3-billion-downloads/|work=The Mozilla blog|access-date=1 November 2013}}</ref>

==References==
{{Reflist|30em}}

==External links==
* [https://addons.mozilla.org/ Official add-on website]
* [https://developer.mozilla.org/Add-ons WebExtensions API reference documentation]
* [https://extensionworkshop.com Extension Workshop, Mozilla's site for Firefox extension developer documentation]

{{Mozilla}}

[[Category:Mozilla]]
[[Category:Firefox add-ons| ]]
[[Category:Free software websites]]