Categories: News

These Weeks In Firefox: Issue 112


  • Picture-in-Picture captions/subtitles support is now enabled by default on Nightly! Supported sites include YouTube, Netflix, Prime Video, and others that use WebVTT
  • The Firefox Profiler supports date format changes according to your locale when viewing your list of published profiles (#3928)
Gif of the Firefox Profiler showing different date formats and locales

Date formats now change depending on the locale.


  • The WebExtensions Framework shows the background event page status in about:debugging and allows you to forcefully terminate the background event page for temporarily installed addons – Bug 1748529
Screenshot of the about:debugging extension card as rendered for an extension with a background event page installed temporarily

View the status of a background script on temporarily installed add-ons, or simply terminate the script if needed.

Friends of the Firefox team

Resolved bugs (excluding employees)

Script to find new contributors from bug list

Volunteers that fixed more than one bug
  • Claudia Batista [:claubatista]
  • Oriol Brufau [:Oriol]
  • Shane Hughes [:aminomancer]
New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions

Addon Manager & about:addons
  • Upcoming changes to the add-on install flow:
    • Introduced some additional cross-origins checks to the add-on installation flows triggered from webpages (both originated by InstallTrigger calls and/or navigations to an XPI url) – Bug 1755950
    • In addition (not landed yet, but should land soon) we also plan to introduce in Firefox >= 100 user activation requirement to successfully trigger the add-on installation flows – Bug 1759737
  • SitePermission add-on type (SitePermission doc page from
    • Allow SitePermission add-ons to be installed from subdomains (along with disallowing the install origin associated to the SitePermission addon xpi file from being set to known eTLD) – Bug 1759764


WebExtensions Framework


WebExtension APIs


Developer Tools

  • WebDriver BiDi – bidirectional protocol for browser automation designed to make cross-browser testing easier. It’s based on a spec.
  • Support for the browsingContext.getTree command has landed, which allows users to get information about all the browsing contexts currently available in the browser.
  • We added support for custom hosts and origins headers for incoming BiDi connections. Thanks to this, the BiDi implementation in Firefox is now compatible with most clients, which is great for end-users as well as for testing. Note that more work is still required for complex setups, for instance using docker.
  • Browser Toolbox – The Browser Toolbox enables you to debug add-ons and the browser’s own JavaScript code rather than just web pages like the normal Toolbox. The Browser Toolbox’s context is the whole browser rather than just a single page on a single tab.
  • Seeking feedback that would help us to understand what features/bugs/workflows are important for its users (mostly folks working on Firefox UI/Add-ons) and prioritize.

Downloads Panel

Form Autofill

Desktop Integrations (Installer & Updater)

  • Thanks to :bhearsum: Landed a good portion of private browsing mode entry point. Aiming for fx-101. Currently pref’d off.
  • Closed bug with background task leaving parts of profile on disk – Kudos to :nrishel:

Password Manager


Performance Tools (aka Firefox Profiler)

  • Move instant markers to the top line in the marker chart panel. (#3927)
  • Capture IPC markers from the unprofiled threads. They will show up in the main thread of their process. (Bug 1709104 and Bug 1755965)
  • Add thread information to the IPC markers that are coming from other threads. (Bug 1758099)
  • Expose frame labels that are interesting to the JS view like “Paint”, “Styles” and GC/CC operations (Bug 1752861)
  • Add SetAnimation, SampleAnimation and ClearAnimation markers on the compositor thread and add more information to the existing animation markers. (Bug 1757202)
  • Reminder: Joy Of Profiling matrix channel and meetings (every monday): come and share your profiles!

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