Firefox 154 release notes for developers (Nightly)
This article provides information about the changes in Firefox 154 that affect developers. Firefox 154 is the current Nightly version of Firefox and ships on August 18, 2026.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
Changes for add-on developers
- Adds support for the
sandboxmanifest key, enabling extensions to designate pages that load with an opaque origin. A sandboxed page can useeval()and similar constructs that are otherwise blocked by the extension's content security policy. The sandboxed page can only access WebExtension APIs or the rest of the extension throughWindow.postMessage(). (Firefox bug 1685123)
Experimental web features
These features are shipping in Firefox 154 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.