Firefox 139.0

By popular request, Full-Page Translations are now available within Firefox extension pages that start with the moz-extension:// URL scheme.

The New Tab custom wallpaper (and colors) option is now available! Your own image can be uploaded as your New Tab wallpaper or any custom color can be selected - from the brightest pink to dark gray. This feature will be rolling out gradually to new users and can also be enabled immediately via Firefox Labs . Additionally, new Wallpaper images and a new Celestial category have also been added.

Link Previews is currently available as an experimental feature which can be enabled via Firefox Labs in the Firefox settings. After enabling, use the Alt+Shift keyboard shortcut when hovering over a link to see the previews in action!

Address autofill has now been enabled for users in Australia and India.

PNG images with transparency now keep their transparency when pasted into Firefox.

The upload performance of HTTP/3 has been significantly improved, particularly on resumed connections (QUIC 0-RTT) and high-bandwidth and high-delay connections.

Due to recent changes in how Chrome encrypts user data on Windows, the Firefox migration wizard can no longer directly import payment methods or passwords from Chrome. However, users can still export passwords from Chrome to a CSV file and then import them into Firefox using the migration wizard or the password manager.

The Review Checker feature is shutting down and will no longer be available after June 10, 2025.

Windows users with certain NVIDIA graphics adapters and multiple monitors running at mixed refresh rates may see graphics corruption after updating to Firefox 139. As a temporary workaround, set the gfx.webrender.dcomp-win.enabled preference to false in about:config and restart Firefox. This issue will be addressed in Firefox 139.0.1.

Various security fixes .

You can find information about policy updates and enterprise specific bug fixes in the Firefox for Enterprise 139 Release Notes .

Developer Information

Based on user requests from both Mozilla Connect and Stack Overflow, the filter setting in the Network panel is now preserved across DevTools Toolbox sessions.

The Debugger's directory root is now scoped to the specific domain where it was set, which aligns with typical usage and avoids applying it across unrelated domains. This builds on previous improvements such as a redesigned UI and easier removal of the root setting. Setting a directory root updates the Source List to show only the selected directory and its children. Learn more

The appearance of the paused line in the Debugger has been refined for better visibility, especially in high contrast mode.

With the release of Firefox 139, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 14 of whom were brand new volunteers! Please join us in thanking each of these diligent and enthusiastic individuals, and take a look at their contributions: adhaliwal34: 1888339

Localized extensions now cascade through locale subtags to find translations before reverting to the extension's default language. Previously, the extension used the extension default if a translation couldn't be found for a language with subtags. See Localized string selection in the Internationalization article for more details of the new behavior. ( Firefox bug 1381580 )

Content scripts and styles are now guaranteed to execute in the order of registration (i.e., their order in the content_scripts manifest key array ). Previously, the order was only guaranteed for scripts within the same js array. ( Firefox bug 1792685 )

The tabGroups API is now available. This API enables extensions to modify and rearrange tab groups . For more information, see WebExtensions Support for Tab Groups . ( Firefox bug 1940631 )

Prioritized Task Scheduling API (Nightly release). The Prioritized Task Scheduling API provides a standardized way to prioritize all tasks belonging to an application, whether they are defined in a website developer's code, or in third-party libraries and frameworks. This adds support for the scheduler.yield() method and re-enables the whole API in the Nightly release. ( Firefox bug 1958943 , Firefox bug 1920115 ).

View Transition API (Nightly release). The View Transition API has been enabled for SPAs (single-page applications) . It provides a mechanism for easily creating animated transitions between different website views. ( Firefox bug 1950759 ).

Support for escaping < and > in attributes when serializing HTML : dom.security.html_serialization_escape_lt_gt . Firefox now replaces the < and > characters with < and > , respectively, in attributes when serializing HTML. This helps prevent certain exploits where HTML is serialized and then injected back into the DOM. The affected methods and properties are: Element.innerHTML , Element.outerHTML , Element.getHTML() , ShadowRoot.innerHTML , and ShadowRoot.getHTML() . ( Firefox bug 1941347 ).

Disable non-standard beforescriptexecute and afterscriptexecute : dom.events.script_execute.enabled . The events have been disabled on Nightly only, allowing browser testing prior to their removal. The affected events are: beforescriptexecute and afterscriptexecute on the Document interface, and afterscriptexecute and beforescriptexecute on the Element interface. ( Firefox bug 1954685 ).

The Temporal proposal, a better version of Date, is now enabled by default in Firefox.

Timer throttling for Workers is now supported.

Closed <details> elements are now searchable and can be automatically expanded if found via find-in-page.

Firefox now supports the hidden=until-found attribute, allowing content to be found via find-in-page when it's otherwise hidden by default.

window.getSelection().toString() now correctly returns the text serialization when text is selected in a text control, improving cross-browser interoperability on some sites.

Added support for the WebAuthn largeBlob extension .

Added support for requestClose() to HTMLDialogElement .

The built-in editor for contenteditable and designMode now handles collapsible white-space(s) before block boundaries and white-space sequences between visible content more consistently with Chrome. As a result, Gecko no longer inserts a padding <br> element after white-space before a block boundary, aligning behavior with other browsers.

The hidden=until-found HTML attribute and the beforematch event are now supported. The hidden until found state allows you to hide the contents of an element until it is found by user search (for example, using "Find in page") or by fragment navigation. The beforematch event fires just before the hidden attribute is removed ( Firefox bug 1761043 and Firefox bug 1955379 ).

The Temporal API is now supported, this aims to simplify working with dates and times in various scenarios, with built-in time zone and calendar representations ( Firefox bug 1912511 and Firefox bug 1954138 ). This includes:

A duration (difference between two time points): Temporal.Duration

Points in time :

As a unique instant in history:

A timestamp: Temporal.Instant

A date-time with a time zone: Temporal.ZonedDateTime

Time-zone-unaware date/time ("Plain") :

Date (year, month, day) + time (hour, minute, second, millisecond, nanosecond): Temporal.PlainDateTime

Date (year, month, day): Temporal.PlainDate

Year, month: Temporal.PlainYearMonth

Month, day: Temporal.PlainMonthDay

Time (hour, minute, second, millisecond, nanosecond): Temporal.PlainTime

Now (current time) as various class instances, or in a specific format: Temporal.Now

Currently the following calendar types are disabled for the withCalendar() method for PlainDate , PlainDateTime , and ZonedDateTime objects:

islamic

islamic-rgsa

islamic-umalqura

The experimental <discard> element has been removed, along with its corresponding SVGDiscardElement JavaScript interface. These aren't supported in other browsers and are expected to be removed from the specification. ( Firefox bug 1958839 ).

The requestClose() method of the HTMLDialogElement interface is now supported. This allows developers to conditionally prevent a dialog from closing by providing a cancel event handler. ( Firefox bug 1960556 ).

The largeBlob and credProps Web Authentication extensions are now supported, while the prf extension is supported on all desktop platforms. These respectively provide support for large blob storage associated with a credential, additional information about a credential, and a mechanism for generating a random number associated with a credential and a particular input. ( Firefox bug 1795020 , Firefox bug 1844449 , Firefox bug 1935280 ).

The priority manager (on macOS, the background QoS manager) in Firefox, which manages IPC message prioritization between the parent and content processes, has been temporarily disabled for all supported Remote Protocols. This change resolves an issue where, under high system load, initial page loads in newly opened background tabs were not being scheduled, resulting in certain commands hanging ( Firefox bug 1960734 ).

Implemented the emulation.setGeolocationOverride command, allowing tests and automation tools to simulate geographic locations across specified browsing contexts or user contexts. This enables consumers to test location-aware features such as geofencing for local recommendations ( Firefox bug 1954992 ).