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Shoutout to More Layouts – These Weeks in Firefox: Issue 210
28 September 2026 om 21:31
Highlights
- Rév O’Conner added a settings popup to control the layout of the Inspector. “Auto” automatically switches the layout at a given toolbox width.
- The new sidebar (sidebar.revamp) and switcher setting will be enabled by default for users along with Nova in DevEdition, Beta and Release channels. To ease the transition for old sidebar users, the “Open tools from sidebar” option will be unchecked for those users to more closely resemble the old sidebar experience. The migration won’t apply to users who had already tried the new sidebar and reverted back.
- The custom wallpaper library for the New Tab page is coming along! This allows you to save multiple images to your wallpaper folder, rather than replacing one image at a time. While it’s still in development, you can test it by setting
browser.newtabpage.activity-stream.newtabWallpapers.customWallpaper.library.enabledto true, starting in Firefox 157. - Mark added an MDN search engine for Nightly and Developer Edition. Select it from the menus, or type @mdn <search term>.
Friends of the Firefox team
Resolved bugs (excluding employees)
Script to find new contributors from bug list
Volunteers that fixed more than one bug
- :Benjamin Peterson
- Amadi
- any1here
- Caleb Pickard
- Chris Vander Linden
- Gopalarathnam Venkatesan
- Igor [:ExplodingJoysticks]
- Khalid AlHaddad
- Lukáš Lipinský
- Mayank Bansal
- Nazeer Ahmed Shaikh
- Noah Varghese
- Sameem [:sameembaba]
- Sebastian Zartner [:sebo]
- sfshah
- Xiaosen Zhuang
New contributors (🌟 = first patch)
- Amadi:
- Caleb Pickard
- dchen705: Remove unnecessary module import in browser/components/urlbar/tests/browser/head.js
- Ekerin Agboola: Remove old documentation related to the removed SEARCH_SUGGESTIONS_LATENCY_MS histogram
- Igor [:ExplodingJoysticks]:
- Gopalarathnam Venkatesan:
- 🌟 Jieke Jiang: Remove unused AboutReaderParent._getArticle
- 🌟 Andrew: White flash on startup caused by abouthome_cache storing incompatible startup frame
- 🌟 Rév O’Conner: Inspector does not respect panel layout
- 🌟 Kana: browser_privatebrowsing_resetPBM.js awaits an array instead of Promise.all, so the tab-close wait does nothing
- Raúl: L10nCache.add() throws on an unknown Fluent ID instead of reporting it
- 🌟 Samuel Mbabhazi: Use new color syntax throughout the DevTools
- K: “Go to line” sets a cursor line which does not exist in footer location indicator
- sfshah:
- Nazeer Ahmed Shaikh
- Noah Varghese:
- Valerie Racine (:v-racine): Fix incorrect assertion message in browser_adoptTab_failure.js
- 🌟 Xiaosen Zhuang:
Project Updates
Add-ons / Web Extensions
Addon Manager & about:addons
- As part of Project Nova related work:
- Fixed responsive layout issues that caused horizontal scrolling in about:addons at high zoom levels – Bug 2059864
- Fixed the “Discover extensions” button appearing multiple times in about:addons – Bug 2070281
- Added telemetry for theme-picker shown events and for appearance/native-theme changes in about:addons – Bug 2069417 / Bug 2070341
- Added an accessible name to the themes mode control in about:addons, fixed in Firefox 158 and uplifted to the Firefox 157 beta channel – Bug 2064563
- Thanks to Mark Kennedy for the help on fixing this accessibility gap
- Updated the built-in dark and light theme previews to use the nova style – Bug 2070274
- Thanks to Emilio Cobos Álvarez for the fix to the default light and dark theme previews.
- Fixed the Nova default and AMO curated theme previews to follow the OS light/dark mode while ignoring the Website appearance setting, fixed in Firefox 158 and uplifted to the Firefox 157 beta channel – Bug 2070562
- Stopped setting unused taarId session cookies for AMO on startup – Bug 1871561
- Thanks to Manuel Bucher for helping us to clean up these unused internals.
WebExtension APIs
- Fixed webRequest requestBody parsing so POST form fields named __proto__ are no longer dropped – Bug 2061470
- Changed alarms.clearAll() to resolve with undefined instead of a boolean, starting in Firefox 157 – Bug 2067229
- Thanks to Ollie Hensman-Crook for the fix to the alarms API.
- Implemented native messaging support via xdg-native-messaging-proxy for Flatpak and Snap builds – Bug 1955255
- Thanks to Jan Horak for the native messaging work on Linux packaging.
- As part of Florian Quèze effort to investigate and fix intermittent failures:
- Made windows.update() wait for the window to actually resize or move before resolving, fixing an intermittent Linux test failure – Bug 1307759
- Fixed a pageAction popup incorrectly opening via a commands API shortcut while the extension was already shutting down – Bug 2039637
- Fixed action.openPopup() rejecting when a tab hover preview was showing, a regression from Bug 2022281 in Firefox 150, with the fix shipping in Firefox 157 and no uplift planned – Bug 2062229
DevTools
- The team has a few sizable ongoing projects.
- Bomsy is working on moving Stylesheets to the Debugger so we can retire the (XUL-based) Style Editor, and turn the Debugger into a “Sources” panel (keeping all the existing functionality of course). (pref: devtools.debugger.features.stylesheets-in-debugger)
- Alex is investigating ways to better handle CSS authored text and CSSOM changes in the Inspector, building information directly from the Rust CSS engine, with the hope it will bring performance improvement editing styles in the Rules view.
- Nicolas is implementing a way to show to the user how the engine goes from a CSS declaration value to the computed value so it’s easier to follow what’s the result of the different call sites, or how the different units (em, %, vmin, …) are computed to their final (e.g. px) values. (pref: devtools.inspector.css-explainers)
External contributions
- Chris Vander Linden finalized a multi-months project to add a search toolbar in the Netmonitor Raw Response panel, adapting and reusing the component we are using in the Debugger (#1941575)
- Amadi made the “Open in new tab” context menu entry to open tab next to the selected tab, not at the very end of the tab list (#2059979)
- Mayank Bansal optimized the performance of console.clear() (#2068156, #2068157, #2067000)
- Benoit added JSON Lines (JSONL/NDJSON) support in the Netmonitor Response panel (#2059673)
- Gopalarathnam Venkatesan made the “Add class” button (.cls) to be disabled when a class can’t be added to the selected node (e.g. it’s a text node, or a comment, or the doctype node) (#2000150)
- K fixed an issue with the “Go to line” action in the Debugger (#2064575)
- Samuel Mbabhazi refactored our CSS codebase to use new color syntax (e.g. rgb(255 0 0) instead of rgb(255, 0, 0)) (#2054228)
- sfshah turned devtools/client/jsonview/converter-child.js into an ES class (#2004273)
Team/Project Update
- Florian Quèze [:florian] is working on fixing test flakiness in devtools/client/debugger and already landed an impressive stack of patches (#2001947, #2070917, #2070920, #2070932, #2070970, #2027953, #1932082, #2070923, #2070933, #1814093, #1868969, #2071238)
- that also includes fixing various accessibility issues that were spotted by a11y_checks #2070911, #2070955, #2071227, #2071231)
- Note that Julian Descottes [:jdescottes] also has an ongoing quest to reduce intermittent failures in our codebase and fixed a few those last 2 weeks (#1767707, 2069100, #2009386)
- [florian] 24 patches landed on Friday, you can see the impact on https://tests.firefox.dev/tests.html?path=devtools%2Fclient%2Fdebugger
- Nicolas Chevobbe [:nchevobbe] fixed a few issues spotted by Jake in the Inspector for the new-ish attr()CSS function (#2068479, #2068480, #2068483)
- Alexandre Poirot [:ochameau] fixed an OOM crash when viewing source mapped file for a large wasm module with many workers (#2058286)
- Julian Descottes [:jdescottes] improved performance of the Inspector when Devtools was opened on a page with many grid elements (#1988868)
- Hubert Boma Manilla (:bomsy) fixed an infinite loop in the Debugger search if you were searching for $ on a big JS file (#2068517)
WebDriver
- Sameem merged two internal helpers (remote/shared/Sync.sys.mjs and remote/marionette/sync.sys.mjs) which removed some code duplication.
- Khalid AlHaddad unified the navigation commands in Marionette and WebDriver BiDi to always initiate navigations via browsingContext.loadURI().
- Khalid AlHaddad updated the WebDriver BiDi client used by WebDriver tests so that browsing_context.locate_nodes returns the nodes array directly instead of the enclosing result object, matching the updated command response.
- Julian Descottes made the destinationFolder mandatory when calling the browser.setDownloadBehavior command with type=”allowed” – which aligns us with the specification. In order to restore the default behavior without having to specify a folder, clients should call setDownloadBehavior with null instead.
- Henrik Skupin fixed a bug in geckodriver where specifying androidIntentArguments in the capabilities caused the default intent arguments to be omitted.
Fluent
- According to arewefluentyet.com, ~74.77% of our strings are now using Fluent!
Lint, Docs and Workflow
- According to arewemozsrcyet.com, ~59% of our modules are now using moz-src.
- eslint-plugin-mozilla has switched from using Mocha to Jest for tests.
- Planning on future updates to investigate getting devtools & newtab to use the jest installed at the top-level, rather than separately installed copies.
Information Management/Sidebar
- We’re working away on bug fixes for sidebar, vertical tabs, split-view, and Nova
- Thanks Florian (:fqueze) for landing a set of patches that have markedly reduced test flakiness in the Sidebar component
New Tab Page
- Custom wallpaper library
- Dre added a “Your images” folder to the wallpaper picker on the New Tab Page, letting users save and switch between multiple custom wallpapers directly from the picker UI (desktop channels), which reduces friction for users who frequently change backgrounds.
- Dre implemented storage and migration for multiple custom wallpapers so users keep their existing wallpaper during upgrade while gaining the ability to save and switch multiple wallpapers — migration moves old single-wallpaper prefs into the new multi-wallpaper storage and the NTP now reads the wallpaper array at load/sync points.
- Dre updated New Tab Page strings to support multiple custom wallpapers so users now see accurate, localized labels and accessibility text when managing or switching between multiple custom backgrounds, reducing confusion in the UI during wallpaper selection.
- Dre added a delete affordance for saved custom wallpapers inside the New Tab Page picker so users can remove unwanted images from their saved set without going to profile files or prefs, improving manageability of user-provided wallpapers.
- We’ve completed a mass migration of our unit tests from Mocha (not mochi) / Karma to Jest/RTL, which is more modern and actively maintained.
- Sections is now enabled globally for all regions that show the content feed!
- Reem Hamoui fixed Lists widget so that keyboard users can now tab to completed items on the New Tab Page and see a visible selection/focus state
- Reem Hamoui fixed the Timer widget so that keyboard users can toggle focus vs break modes with standard keys (Enter/Space/arrow keys) thanks to restored keyboard handlers and tabindex semantics.
- Reem Hamoui made it so that screenreaders now announce wallpaper names via added aria-labels/alt text and role improvements in the Customize UI.
- Maxx Crawford made it so that the Customize UI now filters wallpapers by their metadata and no longer surfaces images marked hidden or in specific visibility groups.
- Irene Ni added Section Layout Name (String) telemetry to newtab content impression & click events so impressions/clicks now carry layout identifiers for more granular UX and A/B analysis
- Reem Hamoui added accessible names (aria-label/aria-labelledby) to the HNT Customize panel back buttons to fix screen-reader discoverability and keyboard/AT announcement when navigating the New Tab Customize flow.
- Nina Pypchenko [:nina-py] preserved iframe rendering for New Tab Page widgets during drag operations to prevent iframe-backed widgets from going blank while being moved.
- Nina Pypchenko [:nina-py] restored the Stocks widget dropdown and menu visibility under High Contrast Mode by adjusting contrast-aware CSS and ARIA roles so users relying on HCM can access stock controls again.
- Nina Pypchenko [:nina-py] fixed a results text overflow for long search queries in the Stocks widget by adding word-wrap/clamping to result lines, preventing layout breakage and truncated controls when users enter long symbols or queries.
- Nina Pypchenko [:nina-py] added telemetry for theme selection in the New Tab customization panel by emitting a selection ping on change, enabling measurement of user theme choices without changing UX.
- Irene Ni restored the Lists widget switcher checkmark for the selected list by fixing menu item selection-state rendering so users can again see which list is active in the switcher.
- Reem Hamoui updated the Privacy widget CTA and spacing on the New Tab Page, adjusting CSS/layout and CTA copy so the action is more discoverable and has a clearer tap/click target across responsive breakpoints.
- Reem Hamoui updated the zero-state copy for the New Tab Privacy widget to clarify what the widget does and the next steps for users when no privacy events or trackers are present, reducing confusion for first-time or cleared-state users.
- Maxx Crawford landed Fluent strings for the Nova launch New Tab customization callout, enabling localized text in the New Tab customization callout so users in supported locales see translated UI instead of missing-string fallbacks.
- Nina Pypchenko made the customization panel reset when closed, ensuring about:newtab customization state (temporary tile/layout previews) is cleared on close so users no longer see stale previews when reopening the panel.
- Dão Gottwald fixed New Tab to pick up system High Contrast Mode on Linux and macOS, restoring correct high-contrast colors/contrast on those platforms for users who rely on OS-level accessibility settings.
- Irene Ni restored theme matching for New Tab context menus by reapplying theme-aware CSS variables in the New Tab Page contextmenu styles, fixing mismatched colors for users with custom/light/dark themes.
- Dustin Whisman fixed New Tab section context menu button color regression by adjusting the section-contextmenu button style rules (button color variables and state selectors) so section actions now respect theme contrast.
- Irene Ni restored transparency to New Tab card backgrounds by removing opaque background rules so cards correctly display background images/themes and improve visual consistency across DPI/compositing setups.
Picture-in-Picture
- Thanks to Sebastian Zartner [:sebo] for fixing broken Dailymotion captions on the PiP player.
- kpatenio fixed YouTube’s displayed playback speed settings being out of sync with PiP.
- Reminder that the playback speed settings can be enabled with media.videocontrols.picture-in-picture.playback-speed.enabled.
- Thanks to Sylvestre Ledru [:Sylvestre] for helping fix a broken link in our PiP docs as a part of Bug 2071683.
Search and Urlbar
Address Bar
- Dao and Moritz are working on bringing the full urlbar experience into the newtab page, now enabled on nightly and going through polish and improvements.. (Bug 2068104, Bug 2068633, Bug 2069260, Bug 2064747)
- Drew enabled AMP and Wikipedia by default in AT, BE, CH, ES, IE, LU, NL, PL, PT and SE. (Bug 2066294)
- James gated adaptive autofill page results behind a minimum score threshold. (Bug 2066171)
- any1here stopped disabled Manage AI and Labs quick actions being displayed when disabled. (Bug 2070378)
Search
- Dale landed the Recent Searches widget which will be be used launched as an experiment (Bug 2063718)
- Caleb fixed the search box eating the first character typed into it. (Bug 1953361)
- Mark configured Wikipedia search for Sardinian (sc) to use the Sardinian Wikipedia rather than the Italian one. (Bug 2057690)
Places
- Marco fixed bookmarked Google Maps using Google’s default favicon. (Bug 1575809)
- Marco fixed the Downloads and History windows going full-screen instead of floating on macOS. (Bug 2058062)
Tests
- Dashboards:
- Most frequent oranges: https://tests.firefox.dev/intermittent.html#date=21days
- Folders with the most flaky tests: https://tests.firefox.dev/flaky.html?kind=mochitest#date=21days&view=list
- Issues of tests in a given folder: https://tests.firefox.dev/tests.html
- Eg devtools debugger tests shows progress of the recent effort to fix these tests recently
- Flakiness burn down
- Multi-agent Claude sessions running for hours investigating and fixing tests of a given set provided in the prompt. Still iterating on the process. Did this 3 times so far:
- Bug 2062142 – [meta] Fix the flakiness in browser/components/extensions/test/browser
- Top 20 intermittent mochitest bugs annotated by sheriffs.
- Probably what made the mochitest line go down for the first time on https://tests.firefox.dev/
- And what helped with the sidebar component, even though sidebar wasn’t my target.
- Bug 2070797 – [meta] Fix the flakiness in devtools/client/debugger/test/mochitest
- Multi-agent Claude sessions running for hours investigating and fixing tests of a given set provided in the prompt. Still iterating on the process. Did this 3 times so far:
- Profile your claude session for cost and context size: https://github.com/fqueze/claude-profiler
- To monitor cost during your sessions, try https://github.com/padenot/foxtail
