Categories: News

These Weeks In Firefox: Issue 121


Friends of the Firefox team

Resolved bugs (excluding employees)

Volunteers that fixed more than one bug

  • Janvi Bajoria [:janvi01]
  • sayuree
  • Shane Hughes [:aminomancer]

New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions

WebExtensions Framework
    • As part of the ongoing ManifestVersion 3 (MV3) work:
        • The new unified toolbar button is meant to replace the browserAction toolbar buttons but it does not cover all the features that are currently provided by the browserActions toolbar buttons yet. The new toolbar button is currently only enabled when the “extensions.unifiedExtensions.enabled” preference is explicitly set to true in about:config.
        • A huge shout out to both Itiel and James Teh for the great support they provided in the reviews for the unified extensions button!
      • Event Pages (non persistent background pages): In Firefox >= 104, the event page will not be terminated if there is an active connection to a native app through the native messaging APIs (browser.runtime.connectNative and browser.runtime.sendNativeMessage) – Bug 1770696
      • New web_accessible_resources manifest field syntax: In Firefox >= 104, in the “matches” properties of the web_accessible_resources entries in the manifest_version 3 format supports the “<all_urls>” host permission string – Bug 1776841
WebExtension APIs
  • In Firefox >=  104, restricted schemes (eg. “resources” or “chrome” schemes) are allowed in scripting.registerContentScripts API when called from a (MV2) privileged extension – Bug 1756758
  • Fixed a bug with browser.extension.getViews and preloaded browserAction popup pages – Bug 1780008
  • Starting from Firefox 104, the history WebExtensions API will use internal PlacesUtils.history async API
    • Some extensions (e.g. DownThemAll! add-on) were calling the history API during startup and so this fix will also result in a startup performance improvement for Firefox users that have extensions using this API and blocking web requests triggered during the Firefox startup.
    • Huge shout out to Emilio for investigating and fixing this issue!

Developer Tools

  • Many thanks to arai for helping us with instant evaluation issues (bug & bug).
    • Those patches will prevent the following expression to be instantly evaluated as the user is typing
      • [1, 2, 3].map(alert)
  • We fixed a bug for log points in the Browser Toolbox where the logs would only appear if the “Show Content Messages” setting was checked (bug)
  • Julian fixed an issue with debugging addons + reloading (easily triggered when using webext to write your extension) (bug)
    • Uplifted to ESR
  • Bomsy worked on a couple things in the Netmonitor we should improve memory usage and performance
    • Network monitoring is now disabled in the Browser Toolbox until the user selects the  Netmonitor (bug)
    • We now properly clear data when the request list is cleared (bug)
  • Ochameau is still making progress on Debugger source tree stability and performance (bugbugbug and bug, showing decent performance improvements to the Browser Toolbox: DAMP results)
WebDriver BiDi

ESMification status

Lint, Docs and Workflow



  • hiro and florian closed out this bug which can cause the compositor to run at 60hz at all times even when nothing is animating on Windows!
  • emilio made chrome windows support document.visibilityState, which means the refresh driver is now throttled in fully occluded background windows.

Performance Tools (aka Firefox Profiler)

  • Removed the timeline graph type radio buttons (#4147)
    • The "before" state of the Profiler UI is shown, with a section showing the radio buttons for changing the graph type between "Categories with CPU", "Categories" and "Stack height".


    • The "after" state of the Profiler UI is shown. The section showing the graph type radio buttons is gone.


    • If you are a power user and would like to use another timeline graph type, you can call window.toggleTimelineType from the devtools console with various types. See the console message in for more details.
  • Profiler no longer crashes when the profile data is too big, instead we discard only the profile of the child process that was too big, and we log error messages in the JSON file. It’s visible in profile.profileGatheringLog from the console. (Bug 1779685, Bug 1758643, Bug 1779367)
  • Added a power profiling setting to the profiler popup (Power usage data in Watt is available only on Windows 11 with Intel CPUs and Apple Silicon, but the preset can still be used elsewhere for a low overhead profiling of what’s causing thread wake-ups) (Bug 1778282) You can change the profiler setting either via profiler popup or about:profiling.
    • The Profiler settings UI showing a list of radio buttons. Each radio button sets the Profiler into a preset configuration. A new configuration is highlighted for profiling Power Usage.

      This will be very handy for finding power consumption optimizations!

  • Added profiler sub-category for Wasm frames (Bug 1780383)
  • Added doc for local profiling on android with screenshots. Here’s the link to the doc. (#4145)
  • Hid the user interface components showing stacks for tracks that don’t have stack samples (#4133)

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