Categories: News

These Weeks in Firefox: Issue 86


  • Some new printing enhancements have recently landed:
  • dthayer has enabled the skeleton UI on Nightly!
    • This is a Windows-only perceived performance startup optimization that paints the structure of the browser UI very early on during the process lifetime.
    • The dev-platform announcement goes into further detail on how this works, and where to file bugs if you see any
    • Here’s a video demonstration showing the skeleton UI when starting up Firefox on very slow hardware, to better see what’s happening (it usually flashes by quite quickly on fast hardware).
  • Have you recently uploaded a performance profile, and accidentally shared data you didn’t want to? You can now completely delete your profile from the “Uploaded Profile” menu in the top right of the profile viewer

    Delete confirmation popup while deleting the profile

    Delete confirmation popup while deleting the profile.

Friends of the Firefox team


  • [mconley] Welcome mhowell to the front-end team! She’s reporting to bwinton, and will be working on Proton-y things to start

Resolved bugs (excluding employees)

Fixed more than one bug

  • Michelle Goossens
  • Oriol Brufau [:Oriol]
  • Tim Nguyen :ntim

New contributors (🌟 = first patch)

Project Updates

Add-ons / Web Extensions

Addon Manager & about:addons
  • Thanks to emilio’s patch, starting from Firefox 86 the zoom levels for the extensions options pages embedded in the about:addons tabs should be set as expected – Bug 1398481.
WebExtensions Framework
  • Sonia contributed a small but nice cleanup by removing the extensions.webextensions.tabhide.enabled preference. Thanks Sonia!
  • A regression was fixed (introduced by Bug 1638422) related to making sure that webRequest StreamFilter is disconnected after a redirect – Bug 1683189
  • A crash was fixed in webRequests StreamFilter on view-source requests (Bug 1678734)
WebExtension APIs
  • A redirect URI is now allowed to be set to a loopback address in the identity.launchWebAuthFlow API. This was needed to allow extension to successfully integrate OAuth authentication for some common web services (e.g. google services) – Bug 1635344 (landed in Firefox 86, uplifted to 85, will also be uplifted to 78 ESR)

Developer Tools

  • Added an error count button in the Toolbar, which shows the amount of errors on the current page.

    An arrow points to a new error count badge in Developer Tools

    There’s a new error count badge in Developer Tools.

  • Landed a performance fix for the Browser Console (bug)
  • Planned a few upcoming projects:
    • DevTools Fission M3 (reaching feature parity with pre-Fission state)
    • WebDriver BiDi (a standardization project to specify a bidirectional, automation-focused protocol for the future)


New Tab Page

  • New personalization for sponsored content just landed in Nightly, and is having a rollout for Firefox 84/85.
    • This is still all client-side, but uses a topic based interest profile rather than matching on domains in browser history.

Password Manager

  • Thanks to Kenrick85 for their continued contributions, recently landing bug 1579108 to fix alignment in the about:logins item/edit form layout.
  • Dlee and tgiles have been cleaning up about:logins with a series of patches landed:
    • Bug 1678633 – “A blank page is wrongly displayed on the “about:logins” page after signing out from Firefox Sync and checking the option to delete all data”
    • Bug 1679131 – “Remove all confirmation modal – icon and close button icons can be dragged”
    • Bug 1683615 – “about:logins – in-page focus jumps on the meatball menu when navigating by keyboard”
  • Thanks :dao for fixing Bug 1683678 – Mask password button is no longer visible if Light theme is used.


Performance Tools

  • Now you can see the proportion of nursery-allocated strings that were deduplicated on the GC Minor markers thanks to sfink.

    A GCMinor marker tooltip that includes the proportion of nursery-allocated strings that were deduplicated.

    A new GCMinor marker tooltip includes the proportion of nursery-allocated strings that were deduplicated.

  • We improved accessibility in the network chart.



  • Watch this space! Proton is a UI refresh effort that’s just starting to get off of the ground. Expect stylistic and content changes to the toolbars, menus, tabs, etc.
  • Here’s the metabug. All work will fold under it. And here’s the wiki page.
  • There’s a browser.proton.enabled pref, but it’s early days, so this doesn’t do anything right now. As Proton-associated changes land, they’ll be keyed off of this pref.
  • Some things we think we can start working on and landing sooner, so we’re working on that as designs are solidified.

Search and Navigation

  • Fixed a performance problem when a very long search history entry was suggested: Bug 1682434
  • Fixed a race condition where pressing ESC may not always exit search mode: Bug 1677325
  • Fixed a bug causing Bookmarks, Tabs, History buttons to disappear from Search Preferences when restoring defaults: Bug 1681818
  • Removed most browser.urlbar.update2.* prefs in Firefox 86. A few were left for features that are still under consideration: Bug 1665049

2 comments on “These Weeks in Firefox: Issue 86”

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  1. Dalmer Schnur wrote on

    Once again avc codec encoded videos are are broken. Nightly v86, since approx. 1-15-2021.
    Hopeful after each update the issue will be resolved, but so far nothing positive.
    No embedded videos on Twitter produce Video. Audio still works.
    Youtube – according to info for nerds – any video played which has an codec produces audio only.

    Have tested this against Chrome and Opera – Both work correctly
    Tested by turning off Acceleration. – Videos(avc) will play both video and audio, but Nightly becomes extremely unstable with closed tabs showing as a jumbled mess and extreme studdering/freezes. Basically unusable.
    Please address this soon

    *System is Windows 7 64 bit – that should not matter!


  2. jonzn4SUSE wrote on

    Lately I’ve been seen lag issues in Nightly. Just trying to open a new tab or move to another tab, there is a 2-3 second delay that comes and goes.

    Operating System: openSUSE Tumbleweed 20210127
    KDE Plasma Version: 5.20.5
    KDE Frameworks Version: 5.78.0
    Qt Version: 5.15.2
    Kernel Version: 5.10.9-1-default
    OS Type: 64-bit
    Processors: 8 × Intel® Core™ i7-4810MQ CPU @ 2.80GHz
    Memory: 31.0 GiB of RAM
    Graphics Processor: Mesa DRI Intel® HD Graphics 4600


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