Firefox 148 release notes for developers (Beta)
This article provides information about the changes in Firefox 148 that affect developers. Firefox 148 is the current Beta version of Firefox and ships on February 24, 2026.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
APIs
- The
Location.ancestorOriginsproperty is now supported, which enables you to determine whether a document is being embedded in an<iframe>and, if so, by which site(s). (Firefox bug 1085214).
Changes for add-on developers
Experimental web features
These features are shipping in Firefox 148 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.
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Document Picture-in-Picture API (Nightly):
dom.documentpip.enabledThe Document Picture-in-Picture API makes it possible to open an always-on-top window that can be populated with arbitrary HTML content such as a video with custom controls or a set of streams showing the participants of a video conference call. (Firefox bug 1858562).