Firefox 147 release notes for developers (Beta)
This article provides information about the changes in Firefox 147 that affect developers. Firefox 147 is the current Beta version of Firefox and ships on January 13, 2026.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
CSS
- The
-webkit-prefixed version of theperspectiveproperty is now supported with unitless values — for example-webkit-perspective: 800— for increased compatibility. (Firefox bug 1362499). - View transition types are now supported, which provide a mechanism by which different types can be specified for active view transitions. CSS can then be used to apply animations to DOM elements when their content updates, depending on the transition type specified. Firefox 147 adds support for single-page app (SPA) view transition types only, not cross-document view transition types. (Firefox bug 2001878).
- The
counter-increment,counter-reset,counter-set, andquotesproperties are now supported on the::markerpseudo-element. (Firefox bug 2000404).
APIs
-
The
Document.activeViewTransitionproperty is now supported, which returns aViewTransitioninstance representing the view transition currently active on the document. This provides a consistent way to access an active view transition in any context without having to manually store a reference to it for later use. (Firefox bug 2001836). -
WebGPU API support is now enabled for all macOS versions on devices with Apple Silicon processors (previously only macOS Tahoe support was enabled). (Firefox bug 1993341).
-
The Navigation API is now supported. This provides the ability to initiate, intercept, and manage browser navigation actions, and to examine an application's history entries. This is a successor to previous web platform features such as the History API and
window.location, which solves their shortcomings and is specifically aimed at the needs of single-page applications (SPAs). (Firefox bug 1997962).
Changes for add-on developers
Experimental web features
These features are shipping in Firefox 147 but are disabled by default.
To experiment with them, search for the appropriate preference on the about:config page and set it to true.
You can find more such features on the Experimental features page.