Firefox 133.0

Firefox now has a new anti-tracking feature, Bounce Tracking Protection, which is now available in Enhanced Tracking Protection's "Strict" mode. This feature detects bounce trackers based on their redirect behavior and periodically purges their cookies and site data to block tracking.

The sidebar to view tabs from other devices can now be opened via the Tab overview menu .

Canvas2D switched from Direct2D to a platform independent acceleration backend on Windows.

The “Picture-in-Picture: auto-open on tab switch” feature from Firefox Labs now behaves more reliably across a wider range of sites, automatically opening relevant videos while ignoring others.

When server time is available, the "expire" attribute value is adjusted by adding the difference between the server and local times. If the current time is set in the future, cookies that have not expired according to the server time are considered valid.

Various security fixes.

You can find information about policy updates and enterprise specific bug fixes in the Firefox for Enterprise 133 Release Notes .

Developer Information

Firefox now supports the keepalive option in the Fetch API . This feature allows developers to make HTTP requests that can continue to run even after the page is unloaded, such as during page navigation or closing.

Firefox now supports the Permissions API in Worker Context.

Firefox now dispatches beforetoggle events just before a dialog opens and toggle events after the dialog closes, matching the behavior of popovers .

Methods are now available on UInt8Array to convert to and from Base64 and hexadecimal encodings. This is an implementation of a Stage 3 TC39 proposal, for more details see the proposal text .

Added support for image decoding as part of the WebCodecs API . This allows for decoding of images from the main and worker threads.

With the release of Firefox 133, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 16 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: abhijeetchawla[:ff2400t]: 1810429 , 1810480 , 1810482 , 1810483 , 1810485 , 1810486 , 1855165 , 1855168

cookies.get now orders cookies according to the 5.4 The Cookie Header section of the HTTP State Management Mechanism (RFC 6265) . This impacts call results when a cookie has variants with different path components. Previously, the earliest created cookie was matched by cookies.get , cookies.remove , cookies.set , and cookies.getAll . After this change, the cookie with the longest matching path is returned. ( Firefox bug 1798655 )

Fixed a bug in the declarativeNetRequest API that prevented rule registration after a browser restart ( Firefox bug 1921353 ). This bug affected extensions that rely on declarativeNetRequest.updateDynamicRules or declarativeNetRequest.updateEnabledRulesets . This fix has also been backported to Firefox ESR 128.5 and Firefox ESR 115.18.

Fixed a bug that prevented window.close() called from a sidebar from closing the sidebar.

contenteditable plaintext-only value: dom.element.contenteditable.plaintext-only.enabled . The plaintext-only value of the contenteditable global attribute indicates that the element is editable; rich text formatting is disabled and any formatting in pasted text is automatically stripped. ( Firefox bug 1922723 .)

:has-slotted CSS pseudo-class: layout.css.has-slotted-selector.enabled . The :has-slotted pseudo-class is used to style elements in <template> that have content added to a <slot> element when rendering a web component . ( Firefox bug 1921747 .)

The viewport <meta> tag now supports the interactive-widget attribute, this influences the size of the viewport when common UI widgets, such as virtual keyboards, are added to the screen. ( Firefox bug 1831649 and Firefox bug 1920755 ).

Support for Uint8Array methods to ease conversions between base64 - and hex-encoded strings and byte arrays. ( Firefox bug 1917885 and Firefox bug 1862220 ). The new methods include:

Uint8Array.fromBase64() and Uint8Array.fromHex() static methods for constructing a new Uint8Array object from a base64- and hex-encoded string, respectively.

Uint8Array.prototype.setFromBase64() , and Uint8Array.prototype.setFromHex() instance methods for populating an existing Uint8Array object with bytes from a base64- or hex-encoded string.

Uint8Array.prototype.toBase64() and Uint8Array.prototype.toHex() instance methods, which return a base64- and hex- encoded string from the data in a Uint8Array object.

The WorkerNavigator.permissions property is now supported, allowing the Permissions API to be used in workers as well as the main window thread. ( Firefox bug 1193373 ).

The EventSource interface to handle server-sent events is now supported in service workers . ( Firefox bug 1681218 ).

The ImageDecoder , ImageTrackList , and ImageTrack interfaces of the WebCodecs API are now supported, enabling the decoding images from the main and worker threads. ( Firefox bug 1923755 ).

The beforetoggle and toggle events of the HTMLElement interface are now fired at <dialog> elements immediately before and after they are shown or hidden, respectively. The beforetoggle can be used, for example, to apply/remove classes that control the animation of a dialog, or reset the state of a dialog form before it is shown. The toggle event can be used to get change notification of the open state, which otherwise requires a MutationObserver . ( Firefox bug 1876762 ).

The keepalive initialization option to the global fetch() method and the Request() constructor are now supported, along with the Request.keepalive property. keepalive can be set to true to prevent the browser from aborting the associated request if the page that initiated it is unloaded before the request is complete. This might be used, for example, to send analytics at the end of a session, even if the user navigates away from or closes the page. Using fetch() with keepalive has some advantages over using Navigator.sendBeacon() for the same purpose, such as allowing the use of HTTP methods other than POST , customizable request properties, and access the server response via the fetch Promise fulfillment. It is also available in service workers . ( Firefox bug 1906952 , Firefox bug 1923044 ).

The onwaitingforkey content attribute can now be specified on <audio> / <video> elements to set an inline event handler for the waitingforkey event. ( Firefox bug 1925952 ).

ServiceWorkerContainer is now exposed in all worker contexts via WorkerNavigator.serviceWorker , allowing workers to inspect and manage the service worker registrations associated with the current origin. Previously ServiceWorkerContainer was only available in the main thread, via Navigator.serviceWorker . ( Firefox bug 1113522 ).

The name property of PerformanceNavigationTiming now omits text fragments from the returned URL, matching the specification. This kind of PerformanceResourceTiming object is returned by Performance.getEntries() for entries with an entryType of navigation . ( Firefox bug 1919565 ).

The options.shadowRoots argument for passing ShadowRoot objects to the Document.caretPositionFromPoint() method has been withdrawn from the release. The feature can be tested in the Nightly release and is expected to re-release in future. ( Firefox bug 1914596 ).

Added support for the url argument for the network.continueRequest command, allowing requests to be transparently redirected to another URL ( Firefox bug 1898158 ).

Updated browsingContext.print to throw an InvalidArgumentError when used with incorrect dimensions ( Firefox bug 1886382 ).

Fixed script.evaluate and script.callFunction to allow the use of document.open in sandbox realms ( Firefox bug 1918288 ).

Fixed a bug where the browsingContext.load event might contain the wrong navigation ID if a same-document navigation occurred during the main navigation ( Firefox bug 1922327 ).

Fixed another edge case where commands could fail with an UnknownError due to navigation ( Firefox bug 1923899 ).

Updated Marionette to better handle window positioning on Linux with Wayland ( Firefox bug 1857571 ).

Fixed a bug that could leave an empty style attribute on an element when trying to click or clear it ( Firefox bug 1922709 ).

Updated the error message sent for UnexpectedAlertOpen errors to include the text of the corresponding alert ( Firefox bug 1924469 ).