Editing XUL (section)

== History ==

[[File:PeriodicTableofXUL Windows10 PaleMoon31.png|thumb|The Periodic Table of XUL Elements is a reference extension designed to demonstrate XUL's capabilities.]]

XUL was devised at [[Netscape]] in 1997 as part of the development effort that eventually became the [[Mozilla]] [[codebase]].<ref>
{{cite web |url = https://arstechnica.com/information-technology/2004/06/collins-interview/2/ |title = Ars Technica sits down with Scott Collins from Mozilla.org |author = Jorge O. Castro |publisher = Ars Technica |date = 2004-06-15 |access-date=2018-11-28}}
</ref> XUL is similar to web technologies implemented by the [[Gecko (software)|Gecko]] rendering engine. When XUL was introduced, it added features beyond the then standard [[HTML|HTML 4]]. It was designed as an extension of HTML to be used with applications rather than documents.<ref name=essay>{{cite web | url=https://yoric.github.io/post/why-did-mozilla-remove-xul-addons/ | title=Why Did Mozilla Remove XUL Add-ons? |last=Teller |first=David |date=Aug 20, 2020}}</ref>

XUL was used by various Mozilla projects, [[Fork (software development)|forks]] of Mozilla projects, and projects closely related to Mozilla. Some software projects such as [[Songbird (software)|Songbird]], [[Komodo IDE]], and [[Zotero]] started as desktop applications that utilized [[XULRunner]] to render and compose their UI. In the early 2000s, there was some interest in using XUL by other parties, including [[Amazon (company)|Amazon]],<ref>{{cite web|url=http://www.oreillynet.com/pub/a/mozilla/2003/05/02/casestudy2.html |archive-url=https://web.archive.org/web/20120218221243/http://www.oreillynet.com/pub/a/mozilla/2003/05/02/casestudy2.html |archive-date=18 February 2012 |last=King |first=Brian |title=Remote Application Development with Mozilla, Part 2: A Case Study of the Mozilla Amazon Browser (MAB)|work=[[Oreillynet]] |date=2003-02-05 |quote=The Mozilla Amazon Browser is an interesting case study for a number of reasons. First, it's a working prototype application, not an example constructed solely for the purpose of demonstrating the technology. Second, it exercises many areas of Mozilla's support for remote development and thus shows off the capabilities, potential, and limitations of remote XUL applications. Finally, it demonstrates Mozilla's support for web services, an important emerging technology for web application development. }}
</ref> but those have switched over to [[HTML5]].<ref name="life after xul" /><ref name="problems with xul" /> Many of the features of modern web technologies such as HTML5, CSS3, ECMAScript 5+, WebGL, and WebAssembly that made rich and modern web applications possible, without the need of utilizing legacy [[NPAPI]]/[[PPAPI]]/[[ActiveX]] browser plug-in technologies like [[Adobe Flash Player|Adobe Flash]], [[Microsoft Silverlight|Silverlight]], [[Java Web Start|Java]], or [[Adobe Shockwave Player|Shockwave]], also made much of XUL redundant.<ref name=essay/>

Mozilla released Firefox 57, also known as Firefox Quantum, in November 2017. As part of this, Firefox finished transitioning to a multiprocess architecture. Although XUL add-ons could work in this architecture, they often created significant performance issues. Because of this, Mozilla removed support for legacy [[Add-on (Mozilla)|add-ons]], including the use of custom XUL code.<ref name="57rel"/><ref name="2015blog"/> Mozilla switched their browser extensions system to the cross-browser WebExtensions API, which is largely based on the Chrome extension API. In late 2017, Firefox still included 289 XUL bindings for native browser components. By the end of 2019, Mozilla had removed all XUL files from their <code>mozilla-central</code> repository.<ref>{{cite web | url=https://wiki.mozilla.org/Firefox/XUL_and_XBL_Replacement | title=Firefox/XUL and XBL Replacement |access-date=27 September 2022 |last=Grinstead |first=Brian |date=16 December 2019}}</ref><ref name="life after xul">{{cite web|last=Hirsch|first=Jared|date=2 September 2018|title=Life After XUL|url=https://developer.mozilla.org/en-US/docs/Mozilla/Tech/Life_After_XUL:_Building_Firefox_Interfaces_with_HTML|url-status=dead|archive-url=https://web.archive.org/web/20181129013045/https://developer.mozilla.org/en-US/docs/Mozilla/Tech/Life_After_XUL%3A_Building_Firefox_Interfaces_with_HTML|archive-date=29 November 2018|access-date=28 November 2018|website=Mozilla Developer Network (MDN) |publisher=Mozilla}}</ref><ref name = "problems with xul"/>

When Mozilla removed support from Firefox, there were still several applications using XUL. Mozilla began gradually removing XUL support from their email client, [[Mozilla Thunderbird|Thunderbird]]. They released Thunderbird 78 without support for XUL-based extensions in 2020.<ref>{{cite web|url=https://developer.thunderbird.net/add-ons/updating/tb78/changes |title=Adapt to Changes in Thunderbird 69-78 |website=developer.thunderbird.net |access-date=27 September 2022 |date=2022}}</ref>
The [[SeaMonkey]] internet suite chose to re-implement XUL for the Firefox Quantum codebase, and the suite's development has subsequently slowed. The [[Pale Moon]] developers forked Mozilla's entire Firefox 52 ESR codebase to create the Unified XUL Platform [[Pale Moon#Unified XUL Platform (UXP)|(UXP)]] for their [[Goanna (software)|Goanna]] rendering engine. UXP maintains the traditional XUL capabilities.<ref>{{cite web|url=https://forum.palemoon.org/viewtopic.php?f=62&t=17213|title=UXP vs goanna |last=Straver |first=Markus |access-date=27 September 2022 |date=2 November 2017 |quote=The plan is to switch Pale Moon over from our current platform to UXP (long-term plans) because a developed and maintained XUL-based platform is the only way a XUL application (like Pale Moon) has any chance of surviving without falling into obsolescence, with Mozilla abandoning this technology. That has been the main reason why I decided to start on this platform to begin with! Regardless, the platform will not be solely developed for Pale Moon's potential future use, it is developed for any future XUL application that will otherwise be dead in the water. Basically we're taking over the torch from Mozilla in developing and maintaining a platform for XUL applications of any kind; Mozilla should not be seen as "upstream" because it isn't.}}</ref> As a result, Pale Moon and other UXP applications have remained single-process but more extensible compared to modern versions of Firefox and Thunderbird.<ref>{{cite web |title=There is only XUL |url=http://thereisonlyxul.org/ |archive-url=https://web.archive.org/web/20180917071644/http://thereisonlyxul.org/ |archive-date=17 September 2018 |last=Tobin |first=Matt |access-date=18 September 2018}}</ref>