Categories: Uncategorized

These Weeks in Firefox: Issue 95


  • Firefox 89 released this week! This version includes a major UI redesign and thoughtful touches throughout. See the release notes here.
  • We launched, a new platform for the Mozilla community to share their feedback and ideas. While technical feedback and bug reports should still go to Bugzilla, please post product feedback and new feature recommendations to Product managers, engineers, and designers will be engaging with the community there to refine and prioritize the suggestions!
  • Fission is now rolled out to ~50% of Nightly users. For those who don’t yet have it, you can opt-in to using Fission on Nightly, Beta or Release channels by setting `fission.autostart` to `true` followed by a Firefox restart. You will start to see a [F] in the tab hover that confirms that Fission is turned on.
  • We released Total Cookie Protection in private browsing mode in Firefox 89.

Two illustrations. On the left, three hands representating three different websites reach into one jar labelled "Cookies". On the right, the three hands are each reaching into a separate jar.

Friends of the Firefox team

For contributions from May 19 to June 1 2021, inclusive.


Resolved bugs (excluding employees)

Fixed more than one bug

New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions

Addon Manager & about:addons

  • Fixed a small bug in about:addons that was mistakenly allowing a user to remove an extension locked by an enterprise policy – Bug 1658768

WebExtensions Framework

  • Bug 1709687 – NotFoundError: Could not open the file
    • Barret landed a fix to avoid some log spam introduced by the changes originally landed as part of Bug 1649593
  • The id of the extension that is redirecting an intercepted webRequest is now being stored into the channel properties bag (as we are already doing for the extension id that is blocking an intercepted webRequest) – Bug 1711924
    • The devtools are not currently using this new property set on the channel, and so it is not going to be visible anywhere in the UI at the moment, we will be filing a follow up to track it as a possible addition to the DevTools network panel.
  • Gijs fixed a bug that was making Firefox to show the “external protocol permission prompt” when an url for an WebExtension-controlled protocol handler was passed on the command line – Bug 1700976 (originally regressed in Firefox 88 from Bug 1678255)

WebExtension APIs

  • In Firefox 89, the webRequest multipart/form-data parser has been updated to better match the spec (as well as how this API behaves in Chrome) – Bug 1697292

Developer Tools

  • Font preview for HTTP font requests (bug, contributed by Sebastian Zartner, :sebo)

The DevTools Network panel. A font request is highlighted. In a subpanel, samples of the downloaded font are shown.


  • Supporting private fields in DevTools (bug)

The DevTools console. The text representation of a JavaScript Object is expanded. Inside, its properties are listed, including one called #myPrivate.


  • Fission
    • Targeting Fission M8 – reaching feature parity with pre-Fision state. Also focusing on issues related to BFCache changes (changes behind a pref now, but will be enabled in Nightly soon – check: fission.bfcacheInParent)


  • Fission team is fixing the last couple of test failures with the new BFCache in parent process architecture. It is now ready for your testing and experience. Users can set `fission.bfcacheInParent` pref to `true` followed by a Firefox restart to enable this.
  • Please file any Fission bugs you encounter using this template.

macOS Spotlight

  • Work continues on supporting native fullscreen. See bug 1631735. Try the behaviour early by enabling full-screen-api.macos-native-full-screen.
  • Work continues on improved dark mode support. See bug 1623686. Try the behaviour early by enabling widget.macos.respect-system-appearance.
  • Fixed a bug where context menus would sometimes not appear on a two-finger click: bug 1710474.
  • Preliminary work to improve high contrast mode on Mac: Bug 1711261 – Address bar and Search bar lack contrast in OSX High Contrast mode.
  • Preliminary work on reducing power consumption when watching videos.

Messaging System

New Tab Page

  • Work continues on remaining proton redesign work. Meta: Bug 1707989.
    • Continuing to file bugs about this work that include some front-end good first bugs. (:amy is happy to mentor bugs)
  • Bug 1712297 Pinned topsites search shortcuts left hanging when @search_engine gets removed. Fix landed including tests. Thank you :standard8, :aflorinescu & :dao!

Password Manager


Performance Tools

  • You can now filter markers by their category in the marker chart and marker table.
  • No periodic sampling mode now collects thread CPU usage as well. Previously this section was blank. Example profile.

A usage graph in the Firefox Profiler. It shows CPU usage values.

  • When importing a Linux perf profile into Firefox Profiler, the timeline will look better with less wasted empty space. Example profile.
A Firefox Profiler usage graph. Its lines are erratic.


A Firefox Profiler usage graph. Its lines are smooth.


  • Made various improvements on the activity graph in the timeline. It’s more accurate now.


  • Updating site data clearing to also clear storage partitioned by Total Cookie Protection – Bug 1646215

Search and Navigation

  • Drew added new nontechnical address bar overview to source tree documentation, also explaining results composition
  • Drew continues to work on the next Firefox Suggest experiment
  • Daisuke fixed deduplication of search suggestions with the experimental unit conversion address bar provider (browser.urlbar.unitConversion.enabled) – Bug 1711156
  • Daisuke fixed spacing of search shortcut buttons – Bug 1710651
  • Harry fixed the reader view button tooltip – Bug 1712569


  • Kajal Sah started her outreachy internship last week!
  • Kajal is working on a patch to add the screenshot button to the context menu for iframes

Downloads Panel

  • Outreachy intern, Ava Katushka, started with us last week! She’ll be helping us implement fixes and features in the Downloads Panel to make the downloading experience smoother:
    • See meta bug to follow along
    • Work will be behind a pref: (bug 1710929)
  • Ava fixed an issue where downloads telemetry was inflated (bug 1706355).
  • Ava is working on a change where if a user chooses to open a file with a computer application, it’s saved to the Downloads folder (bug 1710933).

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