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Today’s meeting leader is: emalysz

General Topics / Roundtable

  • [standard8] Please ensure your mentored bugs are up to date, and in a clear state for being picked up by potential contributors.Please also take a look at the Firefox and Toolkit mentored bugs where the mentors have now left - are there any bugs you'd be willing to take over mentorship for, or that are just not relevant now?

Friends of the Firefox team


  • [mconley] Welcome Yasmin Shash and Hanna Jones!
  • [vchin] Welcome to Amir who has started as Desktop Integrations EM!

For contributions from September 8th to September 21st 2021, inclusive.

Resolved bugs (excluding employees)

Fixed more than one bug

  • Antonin Loubiere
  • Itiel

New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions

WebExtensions Framework

Downloads Panel


  • A reminder of what Fission is
  • We now have a small set of users on the release channel using Fission!
  • Telemetry so far doesn’t show any problems with stability or performance. We’re keeping an eye on it.


  • Milestone 1 has been completed! All DTDs have been removed from browser.xhtml!

    • As a bonus, this also means that all DTDs have been removed from the startup path, which was a goal for Milestone 2!

    • Are We Fluent Yet?

  • Congratulations to Katherine and Niklas for finally getting us over this milestone!

Form Autofill

High-Contrast Mode (MSU Capstone project)

Lint, Docs and Workflow

macOS Spotlight

  • Window spotlight buttons will now be on the correct side in RTL builds: bugs 1633860 & 1419375.
  • Experimental improvements to video power consumption will land soon in bug 1653417.

    • Fullscreen Youtube video on macOS consumes only 80% of the power it otherwise would.

    • Pref: gfx.core-animation.specialize-video. Expect breakage! For example, controls will not yet appear in fullscreen.

  • We noticed some users unfamiliar with macOS conventions were running Firefox directly from its DMG file. This can result in data loss and slow startup times, since Firefox is not fully installed. We now show a message warning the user in this scenario (bug 516362).

New Tab Page

Nimbus / Experiments

  • Bug 1730924 We want to update the Ajv JSON schema validator in tree

Password Manager

PDFs & Printing


  • Gijs has filed some bugs to make process flipping less likely when Fission is enabled
  • We’ve been seeing a slow but steady decline in the percentage of clients on Nightly seeing tab switch spinners. This might be related to Fission, WebRender, hardware churn, or might be a measurement artifact due to old builds sending telemetry. We’re not sure.
  • Thanks to jstutte for landing a patch that removes some main thread IO during startup when checking if we need to be doing an LMDB migration!

Performance Tools

  • You can now profile a process with only a single click in the about:processes. It will automatically record the 5 seconds and open up the Firefox Profiler UI. Depending on the machines, it can fail if it times out to capture a profile for now. You can use toolkit.aboutProcesses.profileDuration pref to reduce the profiling duration to workaround this for now.
    Example workflow of one-click profiling.

    • [mconley] This is great! Good for getting profiles from users that might not want to enable the full-blown Firefox Profiler toolbar button.

  • Thanks to our contributor, mhansen, Linux perf profiles now include different colors for kernel vs user stack frames.
    Before and after of an example linux perf profile


Search and Navigation

  • Drew enabled the Firefox Suggest offline scenario for en-* users in the US region and made some tweaks to the Address Bar preferences UI
  • Daisuke fixed a regression where the Address Bar was not providing switch-tab results when history results were disabled - Bug 1477895


This week I learned

  • [mconley] We have BrowserTestUtils.waitForMutationCondition, which is really handy for when you want to wait for the DOM to reach some state. Better than TestUtils.waitForCondition since it doesn’t depend on random polling.
  • [kpatenio] You can run startup profile selection menu with local build of firefox using the -P parameter, and that there’s a wiki

    • Example: `./mach run -P`

    • Also handy:

      • `./mach run --profile /tmp/foo` (will create a new profile at that directory or reuse it)
      • `./mach run --temp-profile` (get a brand new profile each time)
      • `./mach run --temp-profile --setpref foo=true --setpref bar=true` (brand new profile and get it into the state for testing a feature)