Backup for a Rainy Day - These Weeks in Firefox: Issue 202

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Mike Conley

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Jun 1, 2026, 2:16:34 PM (18 hours ago) Jun 1
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Hello firefoxd-dev,

A few weeks back (April! Whoops, sorry for the delay!), the Firefox Desktop team got together to talk about the latest goings-on in the codebase. A few of us stuck around afterwards to massage the meeting notes into something a bit more palatable. We hope you find them useful!

Thanks to Katherine Patenio who put these notes together with me.

Backup for a Rainy Day - These Weeks in Firefox: Issue 202

Highlights

  • The profile backup mechanism has been enabled by default for all desktop platforms in Nightly, as well as Beta! The current plan is to have this ride out to Firefox 151 for Windows, macOS and Linux on May 18th!

    • This feature, when enabled, will create a copy of your profile data in the background and store it in a single file on your file system that you can restore from.

    • You will be able to manage this feature in Settings under Sync (for now)

      • [Screenshot]

        • Caption: Firefox settings page showing the Backup feature in dark mode. Backup is enabled, with details of the most recent backup and a “Backup now” button. The page displays the backup file name and a backup location folder path, along with “Choose…” and “Show in folder” buttons. A “Sensitive data” section includes an option to back up passwords and payment methods with encryption, and a disabled “Change password” button.

    • You can read more about the feature here

  • As followups to the recent addition to the WebExtension tabs API to support the new SplitView tabs feature, tabs.group() and tabs.ungroup() have been fixed to work correctly with split view tabs, and fixed split views being prepended instead of appended to tab groups when adopted into a new window - Bug 2029099 / Bug 2029534

  • Adaptive autofill has been enabled on Nightly.

    • Previously, autofill only completed domains (e.g. typing red autofilled reddit.com). Now it can also complete full URLs for pages you visit often (e.g. red → reddit.com/r/firefox), learning from what you actually click in the address bar. If a suggestion isn’t helpful, you can now dismiss it so autofill learns what not to show you too.

  • Markus Stange [:mstange] implemented dynamic toolbar on top in RDM (#1978145), but also implemented some static skeleton UI so it's closer to what we actually have in Firefox for Android

    • dynamic toolbar is behind a pref: devtools.responsive.dynamicToolbar.enabled

    • it can be put on top by setting devtools.responsive.dynamicToolbar.onTop, otherwise it's at the bottom

    • [Screenshot]

      • Caption: Firefox Responsive Design Mode on Desktop displaying the Mozilla homepage in a mobile viewport. The toolbar at the top shows a simulated Android device (including the dynamic toolbar) with a viewport size of 376 × 464 pixels and a device pixel ratio of 3. The page content is shown in French, featuring the Mozilla logo, a “Menu” link, a “Pause animation” button, and the headline “Bienvenue chez Mozilla” with accompanying text about trusted technology and digital rights.

Friends of the Firefox team

Resolved bugs (excluding employees)

Script to find new contributors from bug list

Volunteers that fixed more than one bug

  • Amin Amir

  • aoia7rz7l

  • Chukwuka Rosemary

  • DrSeed

  • Frédéric Wang Nélar

  • japandi

  • John Iweh

  • jonathancabera

  • Josh Aas

  • Keji Bakare

  • kofoworola shonuyi

  • konyhéa

  • liz

  • Mathew Hodson

  • Okhuomon Ajayi

  • Oluwatobi

  • ROSHAAN

  • Sam Johnson

New contributors (🌟 = first patch)


Project Updates

Add-ons / Web Extensions

Addon Manager & about:addons

  • In preparation for the Project Nova restyling of the about:addons page, we have refactored about:addons into separate per-component ES modules, splitting the monolithic aboutaddons.js and aboutaddons.html into 16 dedicated component files under components/ (with no behavior or UI changes) - Bug 2032014

    • NOTE: if you have working on patches with changes to about:addons internals it is very likely you'll need to rebase and solve merge conflicts hit on top of this refactoring, the internals are still largely the same as before but don't hesitate to reach out to the Addons team if you have doubts / questions or need help to figure out how to adapt your patch of top of these changes

WebExtensions Framework

  • Fixed exportFunction to preserve the constructibility of the wrapped function instead of unconditionally making all exported functions implicitly as constructors - Bug 2033173

    • Thanks to Gregory Pappas for contributing this improvement to the Content Scripts' Xray Wrappers helpers!

  • Fixed a Firefox 151 regression where extension content scripts accessing location.ancestorOrigins caused subsequent page script reads of the same property to fail with "Permission denied", breaking sites like Gmail - Bug 2034329

    • Thanks to Simon Farre for promptly investigating and fixing this recent regression!

WebExtension APIs

  • Updated sessions.getRecentlyClosed() to remove the hardcoded cap when maxResults is omitted - Bug 1392125

    • Shoutout to Amine Zroual for contributing this enhancement to the sessions WebExtensions API!

DevTools

  • Artem Manushenkov fixed an issue where autosuggestion popup was removing overridden indicators from properties in the Inspector (#1983408)

  • Andrea Marchesini [:baku] fix DevTools cookie header serialization for long cookies, which could lead to cookies not being visible in Netmonitor (#2031299)

  • Julian Descottes [:jdescottes] fixed a toolbox crash that was happening we couldn't find a localization file (e.g. when using a language pack on Nightly) (#2028930)

  • Nicolas Chevobbe [:nchevobbe] improved @container tooltip so it show the value of variables used in style()(#2030239), has enough contrast in dark mode (#2033782) and contains a link to select the container (#2031688)

    • [Screenshot]

      • Caption: Firefox Developer Tools showing a CSS @container style() rule in the Rules panel. A popover for a <section> element displays container properties including "container-name: hello section-container", "container-type: inline-size", and the custom property "--w: 100px", while indicating that --secondary and --plouf are not set. Below, the container query uses nested var() fallbacks, and a CSS declaration previews the resolved value for background-color.

  • Hubert Boma Manilla (:bomsy) is making good progress on migrating the Console to CodeMirror 6 (#2032758, #2026569)

Fluent

  • We’re now at over 72% of our strings being Fluent! Got a component still using .properties? Convert when you can!

  • [Screenshot]

    • Caption: Stacked area chart titled “Are We Fluent Yet?” showing the number and type of localization strings available in Firefox from 2018 to 2026. The chart tracks Fluent strings (green), Properties strings (blue), DTD strings (pink), and a small number of INI strings. Over time, Fluent strings steadily increase while DTD and Properties strings decline. A tooltip at April 26, 2026 shows 10,372 Fluent strings, 3,997 Properties strings, and no remaining DTD or INC strings, illustrating Firefox’s ongoing migration to the Fluent localization system.

Migration Improvements

New Tab Page

Search and Urlbar

  • Marco has fixed a couple of issues with the places databases to try and improve stability. This should help with avoiding users losing bookmarks or favicons.

  • Work continues on the new separate search bar to improve the functionality, e.g. allowing middle click to perform a search in a new tab, avoiding performing a search when adding a search engine.

  • Work also continues on the new Nova layouts.

Smart Window

  • uplifted 10 bugs to 150.0.1 dot release addressing initial user feedback from diary study and Connect

    • jump to bottom of conversation 2028692

    • stop streaming button 2029204

    • back/forward navigation from assistant 2029229

    • dark mode for various chips 2024499

  • search engine switching from smart bar 2021973

  • Nova styling within smart window 2026794

Storybook/Reusable Components/Acorn Design System

UX Fundamentals

  • The error pages shown when a server sends back an invalid response header or an unsupported content encoding now display accurate, context-specific messages. The invalid response header page also gained a helpful list of next steps. - 2027209

  • In progress: The error page illustrations are being replaced with new artwork, and the system now supports per-illustration size configuration, giving each image the ability to define its own appropriate dimensions. - 2031837

Settings Redesign

Below the fold


This information, including all of the previous updates, are fully available in this doc: https://docs.google.com/a/mozilla.com/document/d/1u9YH3ULNRYg6G-fN-Udkvfkcvg0alJfzi_zIAfFNkL8/edit?usp=sharing

Also note that we’re really just synthesising and humanising the stuff that's on the Wiki, which is freely available from here: https://wiki.mozilla.org/Firefox/Meeting, so check that out if you want the source material. It'll also be posted (minus the Below the Fold stuff) to the Nightly blog.

Finally, if there's a Firefox-ish team that you feel isn't being represented here, please let them know about the above meeting so we can get their updates.

Keep on rockin' the free web,

-Mike

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