Categories: News

These Weeks in Firefox: Issue 58


  • New and wonderful DevTools goodies:
    • New CSS debugging feature coming up soon (likely with Firefox 69): Inactive CSS. This will be tremendously helpful to know when certain CSS declarations don’t have the desired effect and why (join the fun on twitter, check out the bug, demo GIF).
      • The CSS rules pane is showing a helpful infobox explaining why a CSS rule is not being applied.

        The Firefox DevTools will make it much easier to find out why certain styles aren’t being applied!

    • Edit an existing request and running some JS on the response is powerful. Requests can now be formatted in fetch format (in addition to cURL). The created fetch command can also be used directly in the Console. (Bug 1540054, Mrigank Krishan 🌟)
      • The Network Monitor tool shows a request that has a context menu option to re-create that request as a window.fetch command. That command has been automatically put into the console input.

        We’re totally making fetch happen here.

  • User Initiated Picture-in-Picture has been enabled by default on Nightly on Windows
      • A YouTube video with the Picture-in-Picture toggle being displayed over top of it.

        Clicking on the little blue toggle on the right will pop the video out into its own always-on-top player window.

    • See some bugs? Please file them against this metabug
  • Worried about personal information leaking when posting performance profiles from the Gecko Profiler add-on? Now it’s much easier to select exactly what information you share:
      • The new profile publish panel with different data to include/filter out from profile (e.g. hidden threads, hidden time range, screenshots resource URLs and extensions)

        Worried about what’s in those performance profiles you’ve been submitting? Worry no longer!

  • We are now showing an icon in the identity block when a permission prompt got automatically denied by the browser (e.g. because it was lacking user interaction).
  • Cryptomining and Fingerprinting protections have been enabled in Nightly by default in both Standard and Strict content blocking modes.
    • Please file breakage against either of these two bugs

Friends of the Firefox team

Resolved bugs (excluding employees)

Fixed more than one bug

  • Arpit Bharti [:arpit73]
  • Damien
  • Florens Verschelde :fvsch
  • Gary Chen [:xeonchen]
  • jaril
  • Kestrel
  • Nidhi Kumari
  • Oriol Brufau [:Oriol]
  • Richard Marti (:Paenglab)
  • Syeda Asra Arshia Qadri [:aqadri]
  • Tim Nguyen :ntim

New contributors (🌟 = first patch)

Project Updates

Activity Stream

Add-ons / Web Extensions

Developer Tools

  • Adopting Prettier on the DevTools codebase (as a pilot before potentially applying it to more of m-c). This way, we’d have auto-formatting like on C++ code! RFC conversation is here.
  • Continued Rock-solid & Fast Debugging™ work and polishing features landed in 67 and 68 (Worker Debugging, Logpoints, Column Breakpoints)
  • Paused indicator and reason in Debugger is more visible! (Issue 8163, derek-li)
    • The DevTools Debugger is being more obvious that execution is paused, and also is explaining why it's paused (in this case, it's saying "Paused while stepping").

      According to the Debugger, execution is paused because we’re stepping through the code, line-by-line.

  • The Debugger team is showing their GitHub contributors what it’s like to contribute to mozilla-central via Phabricator and Bugzilla directly. Transitioned roughly 12 GitHubbers – really excited about this number!
  • Print emulation landed in Inspector – timely before Earth Day to save the trees 🌲!
  • Reducing some noise, the Browser Console will provide the option to hide content messages (behind devtools.browserconsole.filterContentMessages). Bug 1260877.
  • We’re also adding a way to list all of the elements impacted by a CSS warning in the console. When one of those CSS parser warnings occur inside a rule, the console will find this rule’s selector and let users log the matching elements (bug, demo GIF).
  • Wield more filter power in the Console with the support of regular expressions (bug 1441079, Hemakshi Sachdev [:hemakshis] 🎉)
  • “Race Cache With Network” status is shown for resources in the Network panel (Bug 1358038, Heng Yeow :tanhengyeow)
  • Continued improvements to Responsive Design Mode
  • The new Remote Debugging page is ON (about:debugging). WebIDE and the connect page is slotted for removal. All Debug Targets can be inspected with about:devtools-toolbox.
    • The old Connect page and WebIDE DevTool are riding off into the sunset.

    • Latest features: unplugged USB devices remain in the sidebar as “Unplugged” (bug, screenshot), remote debugging toolboxes show nicer headers with icons depending on what your remote target is (bug, example), and the same tab is reused when you connect again to the same target (bug).
  • Specific resources can be blocked in the network monitor – contributed by the renowned :jryans (bug 1151368) – and the first step to having a fully-fledged resource blocking feature
    • The Network Monitor is showing a network request that was blocked, and a context menu entry to unblock the request.

      Stop, block and roll!



Performance tools

  • Big deploy last week!
  • We show larger screenshots while hovering the screenshots track now.
    • The Firefox Profiler is showing a larger thumbnail when hovering the "Screenshot" timeline track

      Now it’s easier to see what was happening on screen when Firefox was being slow in a profile.

  • Landed splitter for the timeline and detail view.
    • The Call Tree section of the Profiler is being resized via the splitter between the Timeline and the Detail view.

      Ahhh, breathing room.

  • Landed some network panel & tooltip improvements
    • More accessible colors
    • More accurate timing information
    • Graphs for different phases in tooltips
    • MIME types in tooltips
      • A tooltip for a network request is showing timing information and the MIME type for the request.

        The more information we have about a slow Firefox, the easier it is to make Firefox faster.


Policy Engine


  • Prathiksha has started her internship working on streamlining the way we do message passing between about: pages and privileged code, and particularly on about:certerror.
  • Firefox Monitor now enabled by default in Nightly, pending bug 1544875.

Search and Navigation

Quantum Bar

Continuing on fixing regressions in QuantumBar, including improvements for RTL, less visual flicker and lots more.

One comment on “These Weeks in Firefox: Issue 58”

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  1. Vincent wrote on

    Wait, what’s that about a Screenshots track in the Performance tools? I’ve been following this blog for a while, and have never seen any mention of this – if this finally gets added, that would be awesome!


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