# XPInstall > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/XPInstall > Markdown URL: https://mediated.wiki/source/XPInstall.md > Source: https://en.wikipedia.org/wiki/XPInstall > Source revision: 1326435185 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|File format standing for Cross-Platform Install}} {{Infobox file format | name = XPInstall (XPI) | screenshot = | caption = | extension = {{mono|.xpi}} | mime = application/x-xpinstall | owner = [Mozilla Foundation](/source/Mozilla_Foundation) | genre = | container for = | contained by = | extended from = | extended to = }} '''XPInstall''' (Cross-Platform Install) was a technology used by the [Mozilla Application Suite](/source/Mozilla_Application_Suite), [SeaMonkey](/source/SeaMonkey), [Mozilla Firefox](/source/Mozilla_Firefox), [Mozilla Thunderbird](/source/Mozilla_Thunderbird) and other [XUL](/source/XUL)-based applications for installing [Mozilla extensions](/source/Add-on_(Mozilla)) that add functionality to the main application.{{cite web | author=File.org | date=2023-02-24 | title=XPI File: How to open XPI file (and what it is) | website=file.org | url=https://file.org/extension/xpi | access-date=2024-02-23}} Support for XPInstall was removed from Firefox in November 2017 with the release of Firefox 57.{{Cite web |last=Cimpanu |first=Catalin |title=Old Firefox Add-Ons Will Stop Working in Firefox 57, End of 2017 |url=https://www.bleepingcomputer.com/news/software/old-firefox-add-ons-will-stop-working-in-firefox-57-end-of-2017/ |access-date=2025-11-11 |website=BleepingComputer |language=en-us}} == Overview == A XPI (pronounced "zippy" and derived from XPInstall) installer module is a [ZIP](/source/Zip_(file_format)) file that contains an install script or a manifest at the root of the file, and a number of data files. XPI files allowed users to install add-ons, themes, and other extensions to customize their Mozilla applications.{{Cite web |date=2016-10-04 |title=XPI - Mozilla {{!}} MDN |url=https://developer.mozilla.org/en-US/docs/Mozilla/XPI |access-date=2025-11-11 |website=developer.mozilla.org |language=en-US }}{{Dead link|date=December 2025 |bot=InternetArchiveBot }} In early versions of Mozilla (Firefox before 0.7 and Thunderbird before 0.5),{{Cite web |title=CVE-2011-2375 |url=https://vulmon.com/vulnerabilitydetails?qid=CVE-2011-2375 |access-date=2025-11-11 |website=vulmon.com}} the package contained a [JavaScript](/source/JavaScript) install script (install.js) with '''some''' directives for actions to take during an install, including adding files and directories, removing old or obsolete files and directories, executing [command line tools](/source/Command_Line_Tool), etc.{{Cite web |title=CERT/CC Vulnerability Note VU#648758 |url=https://www.kb.cert.org/ |access-date=2025-11-11 |website=www.kb.cert.org}} In later versions of Firefox and Thunderbird, the install script was replaced by a chrome manifest and a [resource description framework](/source/Resource_Description_Framework) file (install.rdf).{{Cite web |date=2016-10-26 |title=Install Manifests - Mozilla {{!}} MDN |url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/Install_Manifests |access-date=2025-11-11 |website=developer.mozilla.org |language=en-US }}{{Dead link|date=December 2025 |bot=InternetArchiveBot }} == Deprecation == In August 2015, Mozilla announced plans to deprecate add-ons based on XUL, XPCOM, and the Add-on SDK in favor of a new [WebExtensions API.](/source/Add-on_(Mozilla)){{Cite web |last=Needham |first=Kev |date=2015-08-21 |title=The Future of Developing Firefox Add-ons |url=https://blog.mozilla.org/addons/2015/08/21/the-future-of-developing-firefox-add-ons |access-date=2025-11-11 |website=Mozilla Add-ons Community Blog |language=en-US}} Mozilla cited several reasons for the transition: * '''Security concerns''': Legacy extensions had unrestricted access to Firefox internals, creating security vulnerabilities * '''Performance issues''': XUL/XPCOM extensions interfered with Firefox's transition to a multiprocess architecture (Electrolysis/e10s) * '''Development complexity''': The tight coupling between Firefox and its add-ons caused development delays and crashes * '''Cross-browser compatibility''': WebExtensions, based on Chrome's extension model, enabled developers to create extensions that worked across multiple browsers === Impact === The transition to Firefox 57 affected thousands of extensions.{{Cite web |last=Brinkmann |first=Martin |date=2017-04-27 |title=If Firefox 57 would be released today, 2273 add-ons would be compatible - gHacks Tech News |url=https://www.ghacks.net/2017/04/27/if-firefox-57-would-be-released-today-2274-add-ons-would-be-compatible/ |access-date=2025-11-11 |website=gHacks Technology News |language=en-US}} Many popular add-ons were rewritten using the WebExtensions API, while others were discontinued because their functionality could not be replicated within the more restrictive WebExtensions framework.{{Cite web |last=Cimpanu |first=Catalin |title=Old Firefox Add-Ons Will Stop Working in Firefox 57, End of 2017 |url=https://www.bleepingcomputer.com/news/software/old-firefox-add-ons-will-stop-working-in-firefox-57-end-of-2017/ |access-date=2025-11-11 |website=BleepingComputer |language=en-us}} The change was controversial within the Firefox community,{{Cite web |title=Mixed Feelings Greet Mozilla's Add-ons Overhaul |url=https://www.infoq.com/news/2015/08/firefox-addons-announcement/ |access-date=2025-11-11 |website=InfoQ |language=en}} with some users and developers praising improved cross-browser compatibility while others criticized the loss of customization capabilities.{{Cite news |title=Firefox 57: Good news? It's nippy. Bad news? It'll also trash your add-ons |url=https://www.theregister.com/2017/11/10/open_source_insider_firefox_57/ |archive-url=https://web.archive.org/web/20250809162629/https://www.theregister.com/2017/11/10/open_source_insider_firefox_57/ |archive-date=2025-08-09 |access-date=2025-11-11 |language=en |url-status=live }} Some users migrated to Firefox forks such as [Pale Moon](/source/Pale_Moon) and [Waterfox](/source/Waterfox), which continued to support legacy extensions.{{Cite web |last=Brinkmann |first=Martin |date=2019-10-25 |title=Waterfox development splits into Classic and Current branches - gHacks Tech News |url=https://www.ghacks.net/2019/10/25/waterfox-development-splits-into-classic-and-current-branches/ |access-date=2025-11-11 |website=gHacks Technology News |language=en-US}} == Legacy == The '''.xpi file extension''' continues to be used for WebExtensions in Firefox. Modern XPI files contain a manifest.json file instead of install.rdf and use the WebExtensions API rather than XUL/XPCOM. Several applications maintained XPInstall support after Firefox discontinued it: * '''[Pale Moon](/source/Pale_Moon)''': Forked Firefox's codebase to create the Unified XUL Platform (UXP), which continues to support traditional XUL extensions * '''[SeaMonkey](/source/SeaMonkey)''': Re-implemented XUL support for newer codebases, though development has slowed * '''[Thunderbird](/source/Mozilla_Thunderbird)''': Gradually transitioned away from XUL-based extensions, removing support in version 78 (2020) == See also == {{Portal|Free and open-source software}} * [Add-on (Mozilla)](/source/Add-on_(Mozilla)) * [XUL](/source/XUL) * [XPCOM](/source/XPCOM) * [Browser extension](/source/Browser_extension) * [Mozilla Archive Format](/source/Mozilla_Archive_Format) == References == {{Reflist}} == External links == * {{cite web | url=https://www.mozilla.org/projects/xpinstall/ | archive-url=https://web.archive.org/web/20090422015912/http://www.mozilla.org/projects/xpinstall/ | archive-date=2009-04-22 | title=XPInstall |access-date=2021-09-28 }} * {{cite web | url=https://developer.mozilla.org/en/docs/Extension_Packaging | archive-url=https://web.archive.org/web/20080819132008/https://developer.mozilla.org/en/docs/Extension_Packaging | archive-date=2008-08-19 | title=Extension Packaging – MDC |access-date=2021-09-28 }} * {{cite web | url=https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/Your_first_WebExtension | title=Your first extension – Mozilla | MDN | access-date=2021-09-28 | date=2021-02-19 }} {{Mozilla projects}} {{DEFAULTSORT:Xpinstall}} Category:Archive formats Category:Firefox add-ons Category:Firefox extensions Category:Installation software Category:Mozilla Category:Package management systems --- Adapted from the Wikipedia article [XPInstall](https://en.wikipedia.org/wiki/XPInstall) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/XPInstall?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.