Firefox 127.0

You can now set Firefox to automatically launch whenever you start or restart your Windows computer. Setting Firefox to auto-launch optimizes efficiency in our browser-centric digital routines, eliminating manual startup delays and facilitating immediate web access. ( Learn more )

We completed work to optimize and enable DNS prefetching for HTTPS documents via the rel="dns-prefetch" link hint. This standard allows web developers to specify domain names for important assets that should be resolved preemptively.

It is now possible to close all duplicate tabs in a window with the Close duplicate tabs command available from the List all tabs widget in the tab bar or a tab context menu.

Firefox will now automatically try to upgrade <img> , <audio> , and <video> elements from HTTP to HTTPS if they are embedded within an HTTPS page. If these so-called mixed content elements do not support HTTPS, they will no longer load.

For added protection on MacOS and Windows, a device sign in (e.g. your operating system password, fingerprint, face or voice login if enabled) can be required when accessing and filling stored passwords in the Firefox Password Manager about:logins page.

To reduce user fingerprinting information and the risk of some website compatibility issues, the CPU architecture for 32-bit x86 Linux will now be reported as x86_64 in Firefox's User-Agent string and navigator.platform and navigator.oscpu Web APIs.

Links and other focusable elements are now tab-navigable by default on macOS, instead of following macOS' "Keyboard navigation" setting. This is a more accessible default and matches the default in all other platforms. A checkbox in the settings page still allows users to restore the old behavior.

The Screenshots feature in Firefox has gotten a big update! It now supports taking screenshots of file types like SVG, XML, and more as well as various about: pages within Firefox. We've also made the screenshot tool more accessible to everyone by implementing new keyboard shortcuts and adding theme compatibility and High Contrast Mode (HCM) support. And finally, performance for capturing large screenshots has been improved.

Users with a Firefox primary password set should provide this when Firefox 127 first starts. Dismissing the primary password prompt instead will break restoring the previous session, and can disrupt other functionality. This is only required once ( bug 1901899 ). (fixed in 127.0.1)

On Windows, the Private Window icon is displayed in the taskbar even though browser.privateWindowSeparation.enabled is set to false ( bug 1901840 ). (fixed in 127.0.2)

Under certain conditions, YouTube playback may experience stalling issues ( bug 1878510 ). (fixed in 127.0.2)

Various security fixes.

Firefox will now automatically upgrade requests for audio, video, and image subresources from HTTP to HTTPS in secure content, and block HTTP requests for other kinds of media. If an upgraded request fails because the media's host doesn't support HTTPS, the media is not found. This ensures that if content is served securely over HTTPS, then all its subresources are also served securely or not served at all. As pages no longer display mixed content , Firefox has also removed the icon to indicate when a page contains mixed-content, and the mixed-content console warning has been replaced with one that indicates when requests are upgraded. ( Firefox bug 1779757 ).

You can find information about policy updates and enterprise-specific bug fixes in the Firefox for Enterprise 127 Release Notes .

Developer Information

With the release of Firefox 127, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 8 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: alphare33: 1856611

Firefox now installs extensions that specify the "split" value of the manifest.json "incognito" key. However, as Firefox doesn't support split mode and to preserve the integrity of incognito browsing "split" is treated as an alias of the "not_allowed" value ( Firefox bug 1876924 ).

management.ExtensionInfo now returns the install_type of "admin" when an add-on is installed using an enterprise policy ( Firefox bug 1895341 ).

Addition of a filter parameter to declarativeNetRequest.getDynamicRules and declarativeNetRequest.getSessionRules , which enables the list of returned rules to be filtered by ID ( Firefox bug 1820870 ).

host_permissions for Manifest V3 extensions are now displayed to users during installation ( Firefox bug 1889402 ). However, if an extension update requests new host permissions, these are not shown to the user. See ( Firefox bug 1893232 ).

Addition of the runtime.getContexts function that returns information about the contexts associated with the extension ( Firefox bug 1875480 ).

For Manifest V3 extensions, adds fall back to the user-defined shortcuts for the special _execute_browser_action command if there are no user-defined shortcuts for _execute_action . This enables extensions migrating from Manifest V2 to V3 to preserve any user-defined shortcuts for the browser action ( Firefox bug 1797811 ).

Extensions with an embedded options page now support automatic switching to the dark theme based on user preferences ( Firefox bug 1888866 ).

Symmetrical spacing with CSS letter-spacing : layout.css.letter-spacing.model . The CSS letter-spacing property now splits the specified letter spacing evenly on both sides of each character. This is unlike the current behavior where spacing is added primarily to one side ( Firefox bug 1891446 ).

calc() color channel support in relative colors: layout.css.relative-color-syntax.enabled . The CSS calc() function can now parse color channels in relative colors ( Firefox bug 1889561 ).

JavaScript Float16Array typed array : javascript.options.experimental.float16array . Float16Array typed arrays are now supported, along with DataView.prototype.getFloat16() and DataView.prototype.setFloat16() for reading and setting Float16Array values from a DataView , and the Math.f16round() static method that can be used to round numbers to 16 bits. The new type is useful for sharing data with a GPU, in particular for use cases where it makes sense to trade off precision for memory consumption. ( Firefox bug 1833647 .)

navigator.clipboard.read()/write() has been enabled (see documentation ). A paste context menu will appear for the user to confirm when attempting to read clipboard content that is not originated from a same-origin page.

data: and javascript: URLs are now forbidden in the href attribute of the <base> element ( Firefox bug 1850967 ).

Using a <color-interpolation-method> is now supported in gradients created with conic-gradient() , linear-gradient() , and radial-gradient() functions and the repeating-conic-gradient() , repeating-linear-gradient() , and repeating-radial-gradient() functions for repeating gradients ( Firefox bug 1861363 ).

The following Set methods are now supported ( Firefox bug 1868423 ):

Set.prototype.intersection() — Returns a new set containing elements in both this set and the given set.

Set.prototype.union() — Returns a new set containing all elements in this set and the given set.

Set.prototype.difference() — Returns a new set containing elements in this set but not in the given set.

Set.prototype.symmetricDifference() — Returns a new set containing elements that are in either this set or the given set, but not in both.

Set.prototype.isSubsetOf() — Returns a boolean indicating if all elements of this set are in the given set.

Set.prototype.isSupersetOf() — Returns a boolean indicating if all elements of the given set are in this set.

Set.prototype.isDisjointFrom() — Returns a boolean indicating if this set has no elements in common with the given set.

The lh and rlh line height units, first supported in CSS in Firefox 120 , are now supported in SVG as well. They can be used both in CSS property values stroke-width: 0.5lh and SVG attributes values stroke-width="0.5lh" . ( Firefox bug 1892089 ).

The async Clipboard API is now fully supported. The ClipboardItem interface, along with the read() and write() methods of the Clipboard interface, have been enabled. ( Firefox bug 1887845 , Firefox bug 1858788 ).

All HTML character references are now supported in Web Video Text Tracks Format (WebVTT) cues, title text, comments, annotations, and so on. ( Firefox bug 1395924 ).

Fixed support for wheel actions in both WebDriver classic and BiDi to correctly handle modifiers such as ctrl , shift , etc. ( Firefox bug 1885542 ).

Added the permissions.setPermission command which allows to update browser permissions (such as geolocation ). The permissions module is an extension to the WebDriver BiDi specification defined in the Permissions specification ( Firefox bug 1875065 ).

Added support for a11y attributes name and role as locators for the browsingContext.locateNodes command ( Firefox bug 1885577 ).

Added support for the devicePixelRatio argument to browsingContext.setViewport which allows to emulate the behavior of the screens with different device pixel ratio ( Firefox bug 1857961 ).

Improved browsingContext.navigate to avoid race conditions leading to wait unnecessarily before resolving the command ( Firefox bug 1894305 ).

Fixed WebDriver:ElementClear for elements located in a disabled fieldset ( Firefox bug 1863266 ).

Fixed a bug where WebDriver:GetElementText failed to correctly capitalize text containing an underscore ( Firefox bug 1888004 ).

Fixed a bug in WebDriver:SwitchToFrame which could fail if the tab was in the middle of a navigation ( Firefox bug 1817820 ).