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Categories: News

Harder, Better, Faster, Stronger, Prettier – These Weeks in Firefox: Issue 136


Friends of the Firefox team


  • [:mcheang] I’d like to introduce Marc Seibert [:mseibert] our student worker from Berlin! 🥳

Resolved bugs (excluding employees)

Script to find new contributors from bug list

Volunteers that fixed more than one bug
  • CanadaHonk [:canadahonk]
  • Ebilite Uchenna
  • Itiel
  • Noah Osuolale
  • portiawuu
  • Victoria Ajala
New contributors (🌟 = first patch)

Project Updates

Developer Tools

  • External contributors
    • Ivan simplified InactivePropertyHelper#hasVerticalWritingMode (bug)
    • jynk.zilla improved our shared Tab component so selecting a Tab in the overflow panel would make it visible in the Tab bar (bug)
    • omid rad fixed the “copy as cURL” context menu action so the resulting command includes –compressed when the response is compressed (bug)
    • Masashi Hirano added support for BigInt for console API format specifier so we conform to the specification (bug)
      • console.log(“Value: %d”, 42n) -> Value: 42
      • console.log(“Value:”, 42n) -> Value: 42n
  • Contributions from other teams:
    • arai added RegExp static, Function, Intl.Locale and Error.prototype.stack to the eager evaluation allow list (bug)
    • emilio simplified the inspector walker implementation (bug), which brought a nice 10 to 15% improvement in inspector performance tests
  • Alex added a keyboard shortcut to toggle JS tracing (Ctrl+Shift+5) (bug)
  • Alex also made it possible to programmatically toggle the tracer in privileged code (bug)

const {



} = ChromeUtils.import("resource://devtools/server/tracer/tracer.jsm");


startTracing({ prefix: "testPrefix" });



  • Alex cleaned up the debugger frontend redux store (bug, bug), which led to a ~ 15% improvement in Browser Toolbox debugger test
  • Julian introduced and then fixed a bug in Netmonitor for HTTP/3 responses (bug), which he took as an opportunities to add a test for HTTP3, and he’s currently investigating how we could run most of the netmonitor tests with HTTP/3 responses
  • Nicolas fixed a bug where logging/expanding objects in the console would lead to warning messages (bug)
  • Nicolas made it possible to style ::backdrop pseudo-element in the inspector (bug)
    • The Firefox DevTools Inspector is shown with the DOM tree on the left, and the Style pane on the right. A element is being inspected, and a rule matching on the backdrop pseudo-element is displayed setting the background of the dialog to rebeccapurple.

      If your name is “Rebecca”, this one is for you.

WebDriver BiDi
  • Sasha added support for the input.releaseActions command (bug, spec) used to release all the keys and pointer buttons that are currently depressed (via input.performActions)
  • Browsertime performed more tests using the BiDi-based HAR generator, with significantly reduced overhead compared to the DevTools-based solution (bug)
  • Julian fixed an issue on load and domContentLoaded events by using document url instead of document baseUri (bug)
  • Henrik improved navigation timeout error message (bug)

ESMification status

  • Conversions have continued at a good place with some big jumps.
  • Converting modules used in workers is waiting on ES module workers to ship.
  • ESMified status:
    • browser: 60.78%
    • toolkit: 78%
    • Total: 74.6% (up from 66.4%)
  • #esmification on Matrix
  • Migration Document (with a walkthrough!)

Lint, Docs and Workflow

  • The work to separate Prettier from ESLint has now landed.
    • It should generally function in a similar way to before, but your editor won’t complain about formatting issues.
    • If you use VS Code, consider running ./mach ide vscode again which will set the relevant preferences.
  • We are planning on upgrading Prettier, and enabling on xhtml/html/json formats in the Firefox 115 cycle.

Migration Improvements (CalState LA Project)


Search and Navigation

Congrats to our student, Marc for landing his first few bugs on search and address bar! Great job! 🎉

SERP Telemetry
Address Bar

Storybook / Reusable components

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