For example, when requesting 'GET \/index.html', the server may provide information about the availability of a dictionary by returning its path in the header 'Link: <...\/dict>; rel='compression-dictionary''. When the client downloads the dictionary '...\/dict', the server will provide information about its application to HTML files, setting the header 'Use-As-Dictionary: match='\/*html''. On the next request for an HTML resource, such as 'GET \/index2.html', the client will indicate the presence of a dictionary using the header 'Available-Dictionary: dictionary_hash'. If the server has a dictionary with that hash on its side, it will return the contents of index2.html, compressed using that dictionary. <\/p>\n
For delta compression of different versions of JavaScript files in response to the request GET \/app.v1.js, the server can set the header 'Use-As-Dictionary: match='\/app*js'', indicating that the returned content can subsequently be used as a dictionary for paths '\/app*js'. When a file matching this pattern is later requested, such as GET \/app.v2.js, the client will send the hash of the existing dictionary via the header 'Available-Dictionary:', and the server will return only the differences between app.v1.js and app.v2.js. <\/p>\n
![\"Release](\"\/wp-content\/uploads\/2026\/01\/f0c6c38fd79cb5eab26459adbef3cf03.png\")
<\/center>\n- and
- The CompressionStream and DecompressionStream APIs have added support for the Brotli compression format.\n
- In the View Transitions API, used for creating animation effects when switching between different DOM states, a 'type' property has been added, containing an array of transition types. A corresponding CSS selector ':active-view-transition-type' and the document.activeViewTransition property, which returns an instance of the active ViewTransition object for the document, have also been introduced.\n
- A set of CSS properties has been introduced for controlling the display of elements linked to the positions of other elements (CSS Anchor Positioning) without using JavaScript, for example, to attach popover elements that appear similarly to tooltips.\n
- The specification 'Storage Access Headers' has been implemented, defining the request header 'Sec-Fetch-Storage-Access' and the response header 'Activate-Storage-Access' for accessing third-party cookies without invoking the document.requestStorageAccess() method. The server can request access to cookies via the 'Activate-Storage-Access' header, and it will be sent by the client if the user previously confirmed granting access to the cookie storage through the Storage Access API.\n
- The CSS property 'root-font-relative' has been updated to support relative units rcap, rch, rex, and ric.\n
- The Navigation API has been implemented, allowing web applications to intercept navigation operations in the window, initiate transitions, and analyze the history of actions with the application. The API provides an alternative to window.history and window.location properties, optimized for single-page web applications.\n
- In the web development tools, support for editing and adding pseudo-element selectors has been implemented in the CSS rules panel. A button has been added to the interface for viewing data in JSON format for importing resources into the profiling system (Firefox Profiler) to determine information about their size. The inspection panels for HTML elements and animations now display pseudo-elements during View Transitions. The CSS rules panel now shows @position-try rules used to control the display of elements tied to the location of other elements (CSS Anchor Positioning).\n
- In the Firefox version for Android, it has been added protection against attacks<\/a> through third-party channels, such as Spectre, which are used to bypass site isolation. Previously, such protection was only available in desktop builds. <\/ul>\n
- blocks, the use of CSS properties 'counter-*' and 'quotes' has been permitted.\n