Index

Found 168 pages:

# Page Tags and summary
1 Firefox Firefox, Landing, Mozilla
Firefox is Mozilla's popular Web browser, available for multiple platforms including Windows, OS X, and Linux on the desktop and all Android and iOS mobile devices. With broad compatibility, the latest in Web technologies, and powerful development tools, Firefox is a great choice for both Web developers and end users.
2 Australis and add-on compatibility Extensions
We've removed the add-ons toolbar (including the status-bar). You should no longer rely on it existing. There is a shim in place that will attempt to migrate your icons, but it may not work, or only work partially. The best solution is to change the placement of your button. This may also be a good time to wonder if your add-on really needs a toolbar button to be visible by default for all users. Add-ons made using the Add-on SDK should not need to worry about this change.
3 Building Firefox with Rust code Build documentation, Gecko, build, rust
In May 2015 the Rust programming language reached its 1.0 stability milestone, and various experiments with writing parts of Gecko in Rust began. Rust code first shipped in August 2016 with the release of Firefox 48. It became a requirement for building Gecko in February 2017 with Firefox 54.
4 Deploying Firefox in an enterprise environment Deploying Firefox, Deployment, Firefox, Firefox Deployment, Mozilla, Policy Manager, enterprise
Firefox Enterprise documentation is now located on support.mozilla.org.
5 Deploying Firefox in an enterprise environment (before Firefox 60 ESR) Deployment, Firefox, enterprise, for administrators
This page is an attempt to document the process of managing Mozilla Firefox on Windows and macOS computers in the enterprise setting, from start to finish. If you have questions, please e-mail the Enterprise Working Group mailing list at enterprise@mozilla.org. Better yet, subscribe to the list and join in the ongoing discussions.
6 Developer Edition
The Firefox Developer Edition is a version of Firefox that's tailored for web developers. It includes:
7 Reverting Add-ons, Guide, Themes

If you want to use the Developer Edition, but would prefer to use the 'Australis' theme used in Firefox and Firefox Beta, you can switch to the normal Firefox theme: just open the "Customize" panel, click "Themes", and select the theme labeled "Default":
8 Experimental features in Firefox Experimental, Firefox, Preferences, features
This page lists features that are in Nightly versions of Firefox along with information on how to activate them, if necessary.
9 Firefox ESR ESR, Extended Support Release, Firefox for Desktop, LTS, gpo, group policy
Firefox Extended Support Release (ESR) is based on an official release of Firefox for desktop for use by organizations who need extended support for mass deployments. Unlike other release channels, ESRs are not updated with new features every six weeks. They are instead supported for more than a year, updating with major security or stability fixes.
10 Firefox and the "about" protocol Firefox, Guide, Mozilla, Protocols
There is a lot of useful information about Firefox hidden away behind the about: URL protocol. The most useful is the URL about:config, which displays preferences and settings that can be inspected and changed.
11 Firefox developer release notes Firefox, Landing, Mozilla, Release, Release Notes
Below you'll find links to the developer release notes for every Firefox release. These lovingly-crafted notes provide details on what features and APIs were added and improved and what bugs were eliminated in each version of Firefox. All written to give developers like you the information they need most. You're welcome.
12 Firefox 1.5 for developers Add-ons, CSS, DOM, Extensions, HTML, JavaScript, RDF, SVG, Web Development, Web Standards, XML, XML Web Services, XSLT, XUL
Based on the Gecko 1.8 engine, Firefox 1.5 improved its already best in class standards support, and provided new capabilities to enable the next generation of web applications. Firefox 1.5 features improved support for CSS2 and CSS3, APIs for scriptable and programmable 2D graphics through SVG 1.1 and <canvas>, XForms and XML events, as well as many DHTML, JavaScript, and DOM enhancements.
13 Adapting XUL Applications for Firefox 1.5 Add-ons, Extensions, XUL
This page contains a list of changes in Firefox 1.5, affecting XUL developers.
14 Changing the Priority of HTTP Requests HTTP
No summary!
15 Using Firefox 1.5 caching Add-ons, DOM, Extensions, HTML, JavaScript, Web Development
Firefox 1.5 uses in-memory caching for entire Web pages, including their JavaScript states, for a single browser session. Going backward and forward between visited pages requires no page loading and the JavaScript states are preserved. This feature, referred to by some as bfcache (for "Back-Forward Cache"), makes page navigation very fast. This caching state is preserved until the user closes the browser.
16 What's New in Deer Park Alpha API, CSS, DOM, Extensions, Graphics, HTML, JavaScript, SVG
This page is based largely on http://www.squarefree.com/burningedg...eases/1.1.html (thanks Jesse).
17 Firefox 10 for developers Firefox, Firefox 10, Gecko 10
Firefox 10 shipped on January 31, 2012. This article provides information about the new features and key bugs fixed in this release, as well as links to more detailed documentation for both web developers and add-on developers.
18 Updating add-ons for Firefox 10 Add-ons, Extensions, Firefox, Firefox 10, Gecko 10
Although a lot of things have changed in Firefox 10 that, in theory, can cause add-on compatibility breakage, most of them are relatively obscure, so they're not very likely to affect you. This article will help guide you as you update your add-on.
19 Firefox 11 for developers Firefox, Firefox 11
Firefox 11 shipped on March 13, 2012. This article provides information about the new features and key bugs fixed in this release, as well as links to more detailed documentation for both web developers and add-on developers.
20 Firefox 12 for developers Firefox, Firefox 12, Gecko 12, Web Development
Firefox 12 was shipped on April 24, 2012. This page summarizes the changes in Firefox 12 that affect developers. This article provides information about the new features and key bugs fixed in this release, as well as links to more detailed documentation for both web developers and add-on developers.
21 Firefox 13 for developers Firefox, Gecko
Firefox 13 was shipped on June 5, 2012. This page summarizes the changes in Firefox 13 that affect developers.
22 Firefox 14 for developers Firefox, Firefox 14, Gecko, Gecko 14
Firefox 14 shipped on July 17, 2012. This article lists key changes that are useful for not only Web developers to know about, but also Firefox and Gecko developers as well as add-on developers.
23 Firefox 15 for developers Firefox, Firefox 15, Gecko 15
Firefox 15 shipped on August 28, 2012. This article lists key changes that are useful for not only Web developers to know about, but also Firefox and Gecko developers as well as add-on developers.
24 Firefox 16 for developers 2009, Firefox
Firefox 16 shipped on October 9, 2012. This article lists key changes that are useful for not only Web developers to know about, but also Firefox and Gecko developers as well as add-on developers.
25 Firefox 17 for developers 17, Firefox
Firefox 17 shipped on November 20, 2012. This article lists key changes that are useful for not only web developers, but also Firefox and Gecko developers as well as add-on developers.
26 Site Compatibility for Firefox 17 Compatibility, Firefox, Firefox 17, FxSiteCompat, Web Development
This page has been moved to FxSiteCompat.com.
27 Firefox 18 for developers Firefox, Firefox 18
Firefox 18 was released on January 8, 2013. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
28 Site Compatibility for Firefox 18 Compatibility, Firefox, Firefox 18, FxSiteCompat, Web Development
No summary!
29 Firefox 19 for developers Firefox, Firefox 19, NeedsContent
Firefox 19 was released on February 19, 2013. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
30 Site Compatibility for Firefox 19 Compatibility, Firefox, Firefox 19, FxSiteCompat, Web Development
No summary!
31 Firefox 2 for developers Firefox, Firefox 2
Firefox 2 introduces a vast array of new features and capabilities. This article provides links to articles covering the new features.
32 Adding feed readers to Firefox Configuration management
Starting with Firefox 2, Firefox has support for selecting different RSS or Atom feed readers to use when you try to read a feed. This article provides information about how to add support for additional readers not supported by default.
33 Security in Firefox 2 Firefox, Security
This article discusses changes that affect security in Firefox 2.
34 Updating extensions for Firefox 2 Add-ons, Extensions
This article provides information that will be useful to developers that wish to update their extensions to work properly under Firefox 2.
35 Firefox 20 for developers Firefox, Firefox 20, Gecko, Mozilla
Firefox 20 was released on . This article provides information about the changes in this release that will affect developers.
36 Site Compatibility for Firefox 20 Compatibility, Firefox, Firefox 20, FxSiteCompat, Web Development
No summary!
37 Firefox 21 for developers Firefox, Mozilla
Firefox 21 was released on May 14, 2013. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
38 Site Compatibility for Firefox 21 Compatibility, Firefox, Firefox 21, FxSiteCompat, Web Development
No summary!
39 Firefox 22 for developers Firefox, Firefox 22
No summary!
40 Site Compatibility for Firefox 22 Compatibility, Firefox, Firefox 22, FxSiteCompat, Web Development
No summary!
41 Firefox 23 for developers Firefox, Firefox 23
Addons that overlay chrome://browser/content/debugger.xul must now overlay chrome://browser/content/devtools/debugger.xul. You may add references to both these files in chrome.manifest for compatibility.
42 Site Compatibility for Firefox 23 Compatibility, Firefox, Firefox 23, FxSiteCompat, Web Development
This page has been moved to FxSiteCompat.com.
43 Firefox 24 for developers Firefox, Firefox 24
No summary!
44 Site Compatibility for Firefox 24 Compatibility, Firefox, Firefox 24, FxSiteCompat, Guide, Web Development
No summary!
45 Firefox 25 for developers Beginner, Firefox, Firefox 25, Guide
EcmaScript 2015 implementation continues!
46 Site Compatibility for Firefox 25 Compatibility, Firefox, Firefox 25, FxSiteCompat, Guide, Web Development
No summary!
47 Firefox 26 for developers Firefox
Firefox 26 was released on December 10, 2013. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
48 Site Compatibility for Firefox 26 Compatibility, Firefox, Firefox 26, FxSiteCompat, Guide, Web Development
No summary!
49 Firefox 27 for developers Firefox
Firefox 27 was released on February 4, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
50 Site Compatibility for Firefox 27 Compatibility, Firefox, Firefox 27, FxSiteCompat, Guide, Web Development
No summary!
51 Firefox 28 for developers Compatibility, Firefox, Mozilla
Firefox 28 was released on March 18, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
52 Site Compatibility for Firefox 28 Compatibility, Firefox, Firefox 28, FxSiteCompat, Guide, Web Development
No summary!
53 Firefox 29 for developers firefox developers, firefox29
Firefox 29 was released on April 29, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
54 Site Compatibility for Firefox 29 Compatibility, Firefox, Firefox 29, FxSiteCompat, Guide, Web Development
No summary!
55 Firefox 3 for developers Firefox 3
If you're a developer trying to get a handle on all the new features in Firefox 3, this is the perfect place to start. This article provides a list of the new articles covering features added to Firefox 3. While it doesn't necessarily cover every little change, it will help you learn about the major improvements.
56 CSS improvements in Firefox 3 CSS, Firefox 3
Firefox 3 offers a number of improvements to its CSS implementation. While these changes are documented on the appropriate pages in the documentation, this article provides an overview of them all so that developers can easily learn what these changes were.
57 DOM improvements in Firefox 3 DOM, Firefox 3
Firefox 3 offers a number of improvements to the Document Object Model (DOM), especially in regard to support for extensions to the DOM added by other browsers. This article provides a list of those improvements as well as links to more detailed documentation.
58 Full page zoom Extensions, Firefox 3, XUL
Full page zoom (or just fullZoom) is a new feature in Firefox 3.
59 Notable bugs fixed in Firefox 3 Firefox 3
This article offers a list of important bug fixes offered by Firefox 3 that are not necessarily obvious in the documentation.
60 SVG improvements in Firefox 3 Firefox 3, SVG
Firefox 3 offers improved Scalable Vector Graphics (SVG) support over prior versions of Firefox. While these features are documented elsewhere, this article serves as a convenient list so you can easily determine which features were added in Firefox 3.
61 Site compatibility for Firefox 3 Compatibility, Gecko, Web Development
This page tries to give an overview of the changes between Gecko 1.8 and Gecko 1.9, that could possibly affect websites in their behavior or rendering.
62 Templates in Firefox 3 Firefox 3, NeedsContent, NeedsHelp
Templates have been significantly improved in Firefox 3. The key improvement allows the use of custom query processors to handle other types of datasources besides RDF. A new query syntax makes this possible. Built-in support for SQL (mozStorage) and XML datasources is also provided. A full description of the new features available for templates is available. (bug 285631)
63 Updating extensions for Firefox 3 Firefox 3
This article provides information that will be useful to developers that wish to update their extensions to work properly under Firefox 3.
64 Updating web applications for Firefox 3 Firefox 3
There are a number of changes in the upcoming Firefox 3 that may affect your web site or web application, as well as new features you may wish to take advantage of. This article will serve as a starting point as you work on updating your content to take the fullest possible advantage of Firefox 3.
65 Using an external spell checker Extensions, Guide, NeedsExample
Starting with Firefox 3 (as well as Thunderbird 3 and SeaMonkey 2), you can now install an external spell checker using an extension.
66 XUL improvements in Firefox 3 Firefox 3, XUL
Firefox 3 provides a number of new XUL elements, as well as improvements to existing elements. While this material is documented in detail elsewhere, this article provides a convenient list of these improvements as well as links to the detailed documentation.
67 Firefox 3.5 for developers CSS, Firefox, Firefox 3.5, Gecko, Gecko 1.9.1, HTML, JavaScript, Storage, XUL
Firefox 3.5 (released June 30, 2009) introduces a number of new features, as well as additional and improved support for a wide variety of web standards.  This article offers an extensive list, with links to articles covering the major improvements.
68 ICC color correction in Firefox Firefox, Firefox 3, Firefox 3.5
Although support for color correction was introduced in Firefox 3, it was disabled by default, requiring some tinkering about in the about:config window to enable it.  Firefox 3.5 addresses the issues that caused it be disabled by default in the previous version, and now images with International Color Consortium (ICC) tagging are, by default, color corrected.
69 Security changes in Firefox 3.5 Firefox, Firefox 3.5, Security, XUL
This article covers security-related changes in Firefox 3.5.
70 Updating extensions for Firefox 3.5 Extensions
This article provides helpful information to extension developers trying to update their extensions to work properly in Firefox 3.5.
71 Firefox 3.6 for developers CSS, Firefox, Gecko, Gecko 1.9.2, HTML, JavaScript, Namoroka, XUL
Firefox 3.6 offers support for new and developing web standards, increased performance, and an overall better experience for web users and developers. This page provides links to articles covering the new capabilities of Firefox 3.6.
72 Interfaces moved in Firefox 3.6 DOM, Gecko, Gecko 1.9.2, Interfaces, XPCOM
These interfaces were moved to new locations in the tree in Gecko 1.9.2. This is generally only interesting to people doing development on Mozilla itself.
73 Updating extensions for Firefox 3.6 Extensions, Firefox, Firefox 3.6
This article provides helpful information to extension developers trying to update their extensions to work properly in Firefox 3.6.
74 Updating plug-ins for Firefox 3.6 Add-ons, Firefox, Firefox 3.6, Gecko 1.9.2, Plugins
Several changes were made in Gecko 1.9.2 that may impact plug-in developers in particular. This article provides a list of those changes.
75 Updating themes for Firefox 3.6 Firefox 3.6, Themes
This article intends to help theme authors update Firefox-3.5-compatible themes for Firefox 3.6 compatibility.
76 Firefox 30 for developers Firefox, Firefox for Developers
No change.
77 Site Compatibility for Firefox 30 Compatibility, Firefox, Firefox 30, FxSiteCompat, Guide, Web Development
No summary!
78 Firefox 31 for developers Firefox, Firefox 31, Firefox for Developers
Highlights:
79 Site Compatibility for Firefox 31 Compatibility, Firefox, Firefox 31, FxSiteCompat, Guide, Web Development
No summary!
80 Firefox 32 for developers Firefox
Highlights:
81 Site Compatibility for Firefox 32 Compatibility, Firefox, Firefox 32, FxSiteCompat, Guide, Web Development
No summary!
82 Firefox 33 for developers Firefox
Firefox 33 was released on October 14, 2014. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
83 Site Compatibility for Firefox 33 Compatibility, Firefox, Firefox 33, FxSiteCompat, Guide, Web Development
No summary!
84 Firefox 34 for developers Firefox, Releases
Highlights:
85 Site Compatibility for Firefox 34 Compatibility, Firefox, Firefox 34, FxSiteCompat, Guide, Web Development
No summary!
86 Firefox 35 for developers Firefox, Releases
Firefox 35 was released on January 13th, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
87 Site Compatibility for Firefox 35 Compatibility, Firefox, Firefox 35, FxSiteCompat, Guide, Web Development
No summary!
88 Firefox 36 for developers Firefox
Firefox 36 was released on February 24th, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
89 Site Compatibility for Firefox 36 Compatibility, Firefox, Firefox 36, FxSiteCompat, Guide, Web Development
No summary!
90 Firefox 37 for developers Firefox, Release Notes
Firefox 37 was released on March 31st, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
91 Site Compatibility for Firefox 37 Compatibility, Firefox, Firefox 37, FxSiteCompat, Guide, Web Development
No summary!
92 Firefox 38 for developers Firefox, Release
Firefox 38 was released on May 12th, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
93 Site Compatibility for Firefox 38 Compatibility, Firefox, Firefox 38, FxSiteCompat, Guide, Web Development
No summary!
94 Firefox 39 for developers Firefox, Releases
Firefox 39 was released on July 2, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
95 Site Compatibility for Firefox 39 Compatibility, Firefox, Firefox 39, FxSiteCompat, Guide, Web Development
No summary!
96 Firefox 4 for developers CSS, Firefox, Firefox 4, Gecko, Gecko 2.0, HTML, JavaScript, XPCOM, XUL
Firefox 4, which shipped on March 22, 2011, enhances performance, adds more support for HTML5 and other evolving Web technologies, and further improves security. This article provides information about this release and what features are available for Web developers, add-on developers, and Gecko platform developers alike.
97 The add-on bar Add-ons, Extensions, Firefox 4, Guide, NeedsExample, Toolbar
Firefox 4 eliminates the status bar from the bottom of the browser window in favor of a new toolbar located at the bottom of the window. This new toolbar, with the ID "addon-bar", is a standard XUL toolbar; add-ons can insert content into it, and the user can drag buttons into it while customizing their toolbars. This is the primary difference between the add-on bar and the old status bar; you can now put any XUL element into it, since it's a standard toolbar.
98 Firefox 40 for developers Firefox, Releases
Highlights:
99 Site Compatibility for Firefox 40 Compatibility, Firefox, Firefox 40, FxSiteCompat, Guide, Web Development
No summary!
100 Firefox 41 for developers Firefox, Firefox 41, Releases
Highlights:
101 Site Compatibility for Firefox 41 Compatibility, Firefox, Firefox 41, FxSiteCompat, Guide, Web Development
No summary!
102 Firefox 42 for developers 42, Firefox, Mozilla, Release, Release Notes
Highlights:
103 Site Compatibility for Firefox 42 Compatibility, Firefox, Firefox 42, FxSiteCompat, Guide, Web Development
No summary!
104 Firefox 43 for developers Firefox
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 43 was released on December 15, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
105 Firefox 44 for developers Firefox
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 44 was released on January 26, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
106 Firefox 45 for developers Firefox
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 45 was released on March 8, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
107 Firefox 46 for developers Firefox
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 46 was released on April 26, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
108 Firefox 47 for developers Firefox, Release Notes
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 47 was released on June 6, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
109 Firefox 48 for developers Firefox, Release Notes
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 48 was released on August 2, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
110 Firefox 49 for developers Firefox, Release Notes
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 49 was released on September 20, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
111 Firefox 5 for developers Firefox, Firefox 5, Gecko 5.0
Firefox 5, based on Gecko 5.0, was released on June 21, 2011. This article provides links to information about the changes that affect developers in this release.
112 Updating add-ons for Firefox 5 Add-ons, Extensions, Firefox 5
This article provides an overview of the changes you may need to make to your add-ons in order for them to work properly in Firefox 5. You can find a complete list of developer-related changes in Firefox 5 in Firefox 5 for developers.
113 Firefox 50 for developers Firefox, Release Notes
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 50 was released on November 15, 2016. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
114 Firefox 51 for developers Firefox, Mozilla, Release Notes
To test the latest developer features of Firefox,
install Firefox Developer Edition
Firefox 51 was released on January 24, 2017. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
115 Firefox 52 for developers Firefox, Mozilla, Release Notes
Firefox 52 was released on March 7, 2017. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
116 Firefox 53 for developers Firefox, Mozilla, Release Notes
Firefox 53 was released on April 19, 2017. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.
117 Firefox 54 for developers 54, Firefox, Release Notes
Firefox 54 was released on June 13, 2017. This article lists key changes that are useful for web developers.
118 Firefox 55 for developers 55, Firefox, Release Notes
No summary!
119 Firefox 56 for developers 56, Firefox, Release Notes
No summary!
120 Firefox 57 (Quantum) for developers 57, Firefox, Firefox Quantum, Release Notes, Stylo
This article provides information about the changes in Firefox 57 (a.k.a. Firefox Quantum) that will affect developers. Firefox 57 was released on November 14, 2017.
121 Firefox 58 for developers 58, Firefox, Release Notes
No summary!
122 Firefox 59 for developers 59, Firefox, Release Notes
This article provides information about the changes in Firefox 59 that will affect developers. Firefox 59 was released on March 13, 2018.
123 Firefox 6 for developers Firefox, Firefox 6, Gecko 6.0
Firefox 6, based on Gecko 6.0, was released on August 16, 2011. This article provides links to information about the changes that affect developers in this release.
124 Updating add-ons for Firefox 6 API, Add-ons, Firefox
This article provides an overview of the changes you may need to make to your add-ons in order for them to work properly in Firefox 6. You can find a complete list of developer-related changes in Firefox 6 in Firefox 6 for developers.
125 Firefox 60 for developers 60, Firefox, Release Notes
This article provides information about the changes in Firefox 60 that will affect developers. Firefox 60 was released on May 9, 2018.
126 Firefox 61 for developers 61, Firefox, Release
This article provides information about the changes in Firefox 61 that will affect developers. Firefox 61 was released on June 26, 2018.
127 Firefox 62 for developers 62, Firefox, Release
This article provides information about the changes in Firefox 62 that will affect developers. Firefox 62 was released on September 5, 2018.
128 Firefox 63 for developers 63, Firefox, Mozilla, Release
This article provides information about the changes in Firefox 63 that will affect developers. Firefox 63 is the current Beta version of Firefox, and will ship on October 23, 2018.
129 Firefox 64 for developers 64, Draft, Firefox, Mozilla, NeedsContent, Release
This article provides information about the changes in Firefox 64 that will affect developers. Firefox 64 is the current Nightly version of Firefox, and will ship on December 11, 2018.
130 Firefox 7 for developers Firefox, Firefox 7, Gecko 7
Firefox 7 shipped on September 27, 2011. This article provides information about the changes that affect developers -- both of web content and of Firefox add-ons.
131 Updating extensions for Firefox 7 Extensions, Firefox, Firefox 7
This article offers advice for add-on developers that want to update their extensions to work in Firefox 7. Fortunately, most of the changes are relatively minor in this release, and few add-ons should need significant changes to work in Firefox 7.
132 Firefox 8 for developers Firefox, Firefox 8
Firefox 8 was released on November 8, 2011. This article provides information both for web developers and for add-on and Mozilla project developers to help take full advantage of the features of this release.
133 Updating add-ons for Firefox 8 Add-ons, Extensions, Firefox 8, Guide
This article provides information on steps you need to take in order to update your existing add-on for compatibility with Firefox 8. See Firefox 8 for developers for a complete list of everything that changed in Firefox 8.
134 Firefox 9 for developers Firefox, Firefox 9, Gecko 9
Firefox 9 was released for Windows on December 20, 2011. Mac and Linux version 9.0.1, which fixed a crashing bug discovered at the last minute, were released on December 21, 2011.
135 Updating add-ons for Firefox 9 Extensions, Firefox 9, Guide
Firefox 9 doesn't have a lot of changes that should be compatibility issues for add-on developers. However, there are a few possible items that might trip you up, so let's take a look.
136 Headless mode Automation, Firefox, Mozilla, QA, Testing, headless, headless mode, node.js
Headless mode is a very useful way to run Firefox. Just as it might sound, Firefox is run as normal, minus any visible UI components visible. Though not so useful for surfing the web, it comes into its own with automated testing. This article provides all you need to know about running headless Firefox.
137 Index Firefox, Index, Mozilla
Found 164 pages:
138 Linux compatibility matrix
The following table lists the available library versions for the mozilla.org-distributed Firefox builds dependencies, and/or to build Firefox.
139 Multiple Firefox profiles Beginner, Firefox, Guide, Intro, Profiles, QA
A profile in Firefox is the collection of settings, customizations, add-ons, and other personalizations that a user has made or installed into their copy of Firefox. You can find details about profiles on Mozilla's end-user support site.
140 Multiprocess Firefox Elecrolysis, Firefox, Multiprocess, e10s, events
In older versions of desktop Firefox, the entire browser was running in a single operating system process. In particular, the JavaScript that ran the browser UI (also known as "chrome code") used to run in the same process as the code in web pages (also known as "content" or "web content").

Latest versions of Firefox run the browser UI in a separate process from web content. In the first iteration of this architecture, all browser tabs run in the same process and the browser UI runs in a different process. In future iterations, we expect to have more than one content process. The project that's delivering multiprocess Firefox is called Electrolysis, sometimes abbreviated to e10s.
141 Cross Process Object Wrappers
In multiprocess Firefox, chrome code runs in a different process from web content. So chrome code can't directly interact with web content: instead, it must factor out the code that interacts with web content into separate scripts that are called frame scripts.
142 Debugging frame scripts Browser Content Toolbox, Multiprocess Firefox
You can use the Browser Content Toolbox to debug frame scripts. The Browser Content Toolbox is a separate window that includes some of the standard Firefox Developer Tools - specifically: the console, the JavaScript debugger, and Scratchpad - but attaches them to the browser's content process. This means you can debug the frame scripts in your add-on.
143 FAQ
No summary!
144 Frame script environment
The frame script's global is a ContentFrameMessageManager, giving it the following environment:
145 Glossary Glossary
No summary!
146 Limitations of chrome scripts
This page describes patterns that used to work in the chrome process that will no longer work in multiprocess Firefox. These are the sorts of things that will break an old add-on in multiprocess Firefox. The fix is generally some variant of "do that in a frame script loaded into the content process".
147 Limitations of frame scripts
Frame scripts run with system privileges and have access to the Components object, enabling them to use XPCOM objects and JSMs. Many privileged APIs will just work in a content process. Anything that just manipulates data structures will just work. XHR and Workers will work. However, some APIs  that work in the chrome process will not work in a frame script. This article lists the most important of these APIs.
148 Message manager API, Guide, JavaScript
Message managers provide a way for chrome-privileged JavaScript code to communicate across process boundaries. They are particularly useful for allowing chrome code, including the browser's code and extension's code, to access web content while the browser is running web content in a separate process.
149 Communicating with frame scripts
Chrome code and frame scripts communicate back and forth using a messaging API which can include JSON-serializable objects as arguments.
150 Frame script environment
The frame script's global is a ContentFrameMessageManager, giving it the following environment:
151 Frame script loading and lifetime
To load a frame script use the loadFrameScript() function.
152 Limitations of frame scripts
Frame scripts run with system privileges and have access to the Components object, enabling them to use XPCOM objects and JSMs. Many privileged APIs will just work in a content process. Anything that just manipulates data structures will just work. XHR and Workers will work. However, some APIs that work in the chrome process will not work in a frame script. This article lists the most important of these APIs.
153 Message manager overview
This article describes the different types of message manager, how to access them, and at a high level, what sorts of things you can use them for.
154 Performance
This highlights some performance pitfalls related to frame scripts/message manager usage and alternative approaches to avoid them.
155 Process scripts
When you need to run code in the content process in order to access web content, then you should use frame scripts. However, a problem with frame scripts is that they can be loaded multiple times in the content process, in multiple scopes that are insulated from each other. For example, if you call the global frame message manager's loadFrameScript() function, then the script will be loaded separately into all open tabs. This can then cause a problem the frame scripts are interacting with a global service in the content process.
156 Message manager overview
In the initial version of multiprocess Firefox there are two processes:
157 Motivation for Multiprocess Firefox
There are three main reasons for making Firefox run content in a separate process: performance, security, and stability.
158 Pitfalls for add-on developers
This page lists patterns that add-on authors might be using that won't work, or will work differently, in multiprocess Firefox.
159 RemotePageManager Firefox, Multiprocess, Reference, Référence(2)
One of the challenges of converting Firefox features and add-ons to multiprocess Firefox involves in-content pages. These pages (like about:addons) display in a tab but for now still render in the main process. There can be many reasons for wanting to move these into the content process, particularly if the page interacts with web content in any way but more generally just to keep the main UI as responsive as possible.
160 Tab selection in multiprocess Firefox Multiprocess, tab selction
In single-process Firefox, when the user switches tabs, this is a synchronous operation. The browser blocks while it loads content into the newly selected tab, then switches to that tab. It indicates that the tab is selected by setting the selected attribute on the XUL tab object. Code (including browser code, extensions, or themes) that wants to change the appearance of the selected tab can use the selected attribute to apply CSS for that tab.
161 Technical overview Electrolysis, Firefox, Mozilla, Multiprocess, e10s
At a very high level, multiprocess Firefox works as follows. The process that starts up when Firefox launches is called the parent process. Initially, this process works similarly to single-process Firefox: it opens a window displaying browser.xul, which contains all the principal UI elements for Firefox. Firefox has a flexible GUI toolkit called XUL that allows GUI elements to be declared and laid out declaratively, similar to web content. Just like web content, the Firefox UI has a window object, which has a document property, and this document contains all the XML elements from browser.xul. All the Firefox menus, toolbars, sidebars, and tabs are XML elements in this document. Each tab element contains a <browser> element to display web content.
162 Web content compatibility Elecrolysis, Firefox, Guide, Multiprocess, e10s
While the introduction of multi-process capabilities to Firefox should be seamless and invisible to Web content, there are some exceptions and subtle changes from past behavior. This article discusses the known differences you may encounter.
163 Which URIs load where Chrome Process, Content Process
Based initially on the page's URI scheme, the browser can decide whether to load a page in the chrome process or a content process. For some schemes, you can change the default behavior.
164 Performance best practices for Firefox front-end engineers Best practices, Developing Firefox, Developing Mozilla, Firefox, Front-end, Mozilla, Performance
This guide will help Firefox developers working on front-end code produce code which is as performant as possible—not just on its own, but in terms of its impact on other parts of Firefox. Always keep in mind the side effects your changes may have, from blocking other tasks to interfering with other user interface elements.
165 Privacy Privacy, Security
This document lists privacy-related documentation.
166 Storage access policy: Block cookies from trackers Privacy, storage access policy, tracking protection
Pre-release versions of Firefox include a new storage access policy that blocks cookies and other site data from third-party tracking resources. This new policy is designed as an alternative to the current policies offered in release versions of Firefox, and protects against cross-site tracking while minimizing the site breakage associated with cookie blocking. This article explains how the new policy works and how you can test it.
167 Tracking Protection Privacy, Private browsing, blocking, tracking
Starting in version 42, Firefox Desktop and Firefox for Android include built-in tracking protection. In Private Browsing windows (tabs, in Firefox for Android), Firefox will block content loaded from domains that track users across sites.
168 Security best practices for Firefox front-end engineers Best practices, Developing Firefox, Developing Mozilla, Firefox, Front-end, Mozilla, Performance
This article will help Firefox developers understand the security controls in place and avoid common pitfalls when developing front-end code for Firefox.

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