Firefox 136.0

You can now enable the updated Firefox sidebar in Settings > General > Browser Layout to quickly access multiple tools in one click, without leaving your main view. Sidebar tools include an AI chatbot of your choice, bookmarks, history, and tabs from devices you sync with your Mozilla account.

Keep a lot of tabs open? Try our new vertical tabs layout to quickly scan your list of tabs. With vertical tabs, your open and pinned tabs appear in the sidebar instead of along the top of the browser. To turn on vertical tabs, right-click on the toolbar near the top of the browser and select Turn on Vertical Tabs. If you’ve enabled the updated sidebar, you can also go to Customize sidebar and check Vertical tabs. Early testers report feeling more organized after using vertical tabs for a few days.

The Clear browsing data and cookies dialog now allows clearing saved form info separately from browsing history.

Smartblock Embeds allows users to selectively unblock certain social media embeds that are blocked in ETP Strict and Private Browsing modes. Currently, support is limited to a few embed types, with more to be added in future updates.

Firefox now upgrades page loads to HTTPS by default and gracefully falls back to HTTP if the secure connection fails. This behavior is known as HTTPS-First .

On macOS, some background tabs will be moved to lower power cores, reducing energy usage.

Hardware-accelerated playback of HEVC video content is now supported on macOS.

Hardware video decoding is now enabled for AMD GPUs on Linux.

On Linux, Firefox is now available on ARM64 (AArch64), with installation options via APT and tarballs. Flatpak support is coming soon.

The Weather forecast on the New Tab page is expanding to additional regions, including Mexico, Brazil, Argentina, and Chile, as part of an ongoing regional rollout. This feature is part of a progressive roll out. What is a progressive roll out? Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.

Address autofill enabled for users in the United Kingdom. This feature is part of a progressive roll out. What is a progressive roll out? Certain new Firefox features are released gradually. This means some users will see the feature before everyone does. This approach helps to get early feedback to catch bugs and improve behavior quickly, meaning more Firefox users overall have a better experience.

Firefox will now prefer the PNG format when copying images out of Firefox, allowing the preservation of transparency.

For New Tab stories, the Save to Pocket action was moved from a button to the context menu along with other actions, such as Bookmark.

The macOS DMG installer packages now use LZMA for compression, reducing download size and installation time.

Due to recent changes in macOS Sequoia, the shortcut for completing search strings to .com addresses has been changed from Ctrl+Enter to Cmd+Enter.

Users clearing "History" and/or "Site settings" on shutdown on previous versions will also have clearing "Cookies and site data" and "Temporary cached files and pages" enabled after updating to Fx136 even if they previously haven't checked these settings. Affected users can go to "Privacy & Security" settings directly after the upgrade and uncheck both boxes to avoid getting logged out. ( Bug 1952564 )

Various security fixes .

You can find information about policy updates and enterprise specific bug fixes in the Firefox for Enterprise 136 Release Notes .

Developer Information

The Developer Tools debugger editor now uses Codemirror 6, which improves performance.

With the release of Firefox 136, we are pleased to welcome the developers who contributed their first code change to Firefox in this release, 10 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: Arkadiy Tetelman: 1939981

Adds the preferred_environment property to the background manifest key , enabling extensions to request that the browser run their background scripts as a document or service worker ( Firefox bug 1798655 ).

menus.update and menus.remove and the aliases contextMenus.update and contextMenus.remove now reject with an error when the menu item doesn't exist. Previously, the error was ignored and the promise fulfilled. ( Firefox bug 1688743 ).

A new version of the userScripts API is available on desktop Firefox. This version of the API is for use in Manifest V3 extensions and provides broad compatibility with Chrome, although permissions mechanisms differ across the browsers. ( Firefox bug 1943050 ).

The canResume property of downloads.DownloadItem is now set to true when a download fails with NETWORK_FAILED . This enables downloads that fail due to a network error to be resumed using downloads.resume() . ( Firefox bug 1694049 ).

CSS hyphenate-limit-chars property : layout.css.hyphenate-limit-chars.enabled . The hyphenate-limit-chars CSS property is used to specifically the minimum word length for hyphenation as well as the number of characters before and after the hyphen. ( Firefox bug 1521723 ).

Error.captureStackTrace() : javascript.options.experimental.error_capture_stack_trace . The Error.captureStackTrace() static method installs stack trace information on a provided object as the Error.stack property. Its main use case is to install a stack trace on a custom error object that does not derive from the Error interface. ( Firefox bug 1886820 ).

Clear-Site-Data: cache : privacy.clearSiteDataHeader.cache.enabled . The Clear-Site-Data header can be used with the cache or * directives to clear the browser cache. ( Firefox bug 1942272 ).

SVG <discard> element for SVG animations : svg.discard.enabled . The <discard> SVG element allows developers to specify a trigger, such as the elapsed time since the SVG was loaded into DOM or the end of a particular animation, at which a specified element and its children should be removed from the DOM. This allows an SVG viewer to conserve memory by discarding animated elements that no longer needed. ( Firefox bug 1069931 ).

SVG path API methods : dom.svg.pathSegment.enabled . The getPathData() , setPathData() , and getPathSegmentAtLength() methods of the SVGPathElement interface are now supported. These methods provide a convenient way to work with SVG path data instead of parsing raw string data. ( Firefox bug 1934525 ).

Added support for the Intl.DurationFormat object; this enables language-sensitive duration formatting.

Added support for the CSS :open pseudo-class for styling elements that can be toggled “open” to display more content.

Added support for the :has-slotted pseudo-class, allowing authors to style the contents of a <slot> element when it is not empty or not using the default value.

Added support for the CookieStore API , an asynchronous cookie API for scripts running in HTML documents and service workers.

Added support for ARIA elements reflection .

Firefox now sends a referrer from meta refreshes and Refresh headers.

Added support for sending and receiving the AV1 video codec over WebRTC. Both singlecast and simulcast are supported for sending.

Added support for sending multiple simultaneous versions of the same source over WebRTC, commonly called simulcast, with the H264 video codec. H264 is the second video codec after VP8 to be supported for sending simulcast.

The value plaintext-only can now be specified for the contenteditable attribute, making the raw text of an element editable but without supporting rich text formatting.

Added support for the text replacement feature in an input field on macOS. Web content can enable/disable this using the HTML autocorrect attribute.

The autocorrect global attribute allows autocorrection in editable text elements including: most kinds of text <input> elements, <textarea> elements, and elements that have the contenteditable attribute set. The specific autocorrection behavior depends on the user agent and underlying OS. ( Firefox bug 1927977 ).

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 1922724 ).

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 1940691 ).

The :open pseudo-class is now supported and allows you to select any element that is currently in an open state, this applies to the <details> , <dialog> , <input> elements with a picker and <select> elements which present a drop-down box. ( Firefox bug 1936113 ).

The <gradient> CSS functions linear-gradient() , conic-gradient() , and radial-gradient() now allow a single color stop and 0-1 positions. This produces a single solid color and is used in setting the mask CSS property. ( Firefox bug 1900530 ).

Intl.DurationFormat is now supported, enabling locale-sensitive formatting of durations. ( Firefox bug 1933303 ).

The Referer HTTP header is now sent in requests following a page refresh that redirects to a new page (if permitted by the Referrer-Policy ), and document.referrer will be set to the referrer URL after navigating. The page refresh may be triggered by the Refresh response header, or equivalent <meta> in markup (for example <meta http-equiv="refresh" content="3;url=https://www.mozilla.org" /> ). Note that same-page refreshes are treated as same-page navigation to a page fragment: since the page isn't re-requested, Referer isn't sent. ( Firefox bug 1928291 )

The maximum size of Data URLs has been increased from 32MB to 512MB, matching the limit for Chromium browsers ( Firefox bug 1911300 ).

Element properties are now reflected for the Aria attributes that contain element references ( Firefox bug 1919102 ). This includes:

ariaActiveDescendantElement , ariaControlsElements , ariaDescribedByElements , ariaDetailsElements , ariaErrorMessageElements , ariaFlowToElements , ariaLabelledByElements , ariaOwnsElements in the Element interface

ariaActiveDescendantElement , ariaControlsElements , ariaDescribedByElements , ariaDetailsElements , ariaErrorMessageElements , ariaFlowToElements , ariaLabelledByElements , ariaOwnsElements in the ElementInternals interface.

WebRTC can now send and receive video encoded using the AV1 codec . When sending, it can be used for both sending multiple simultaneous versions of the same source (" simulcast ") and singlecast. ( Firefox bug 1944878 and Firefox bug 1932065 ).

WebRTC simulcast of screen-shared video with the H264 codec is also supported (AV1, H264, and VP8 can now be used for simulcast). Note that the H264 codec is hardware-enabled on Android. ( Firefox bug 1210175 ).

WebRTC support for the Dependency Descriptor (DD) RTP Header Extension , and its use with AV1, VP8, and VP9 codecs. The DD header extension enables codec-independent forwarding of simulcast streams, including in scenarios where the payload is end-to-end encrypted (E2EE). ( Firefox bug 1945261 ).

Firefox now handles WebSocket port conflicts for the RemoteAgent more efficiently. If the port specified via the --remote-debugging-port command line argument cannot be acquired within 5 seconds, such as when another Firefox process is already using it, Firefox will now shut down instead of hanging ( Firefox bug 1927721 ).

Navigations using the HTTP scheme, triggered by the WebDriver:Navigate command in Marionette or browsingContext.navigate in WebDriver BiDi, will no longer be automatically upgraded to HTTPS. These requests will now remain on HTTP as intended ( Firefox bug 1943551 ).

The session.subscribe command now returns a subscription ID, which can be used with session.unsubscribe to precisely target the same previously subscribed events and contexts as the original subscription. This helps prevent unintended side effects when multiple subscriptions exist, such as those limited to a specific tab ( Firefox bug 1938576 ). Note: The previous logic for removing events by name and context has been deprecated and will be removed in a future release.

Added support for the userContexts field in the script.addPreloadScript command, allowing clients to specify in which user contexts (containers) the script should always be loaded automatically, including any new browsing contexts opened within such specified user contexts ( Firefox bug 1940927 ).

The browsingContext.contextDestroyed event now returns a fully serialized browsing context tree when a context is closed, including all its child contexts ( Firefox bug 1860955 ).