Firefox 156 release notes for developers (Nightly)
This article provides information about the changes in Firefox 156 that affect developers. Firefox 156 is the current Nightly version of Firefox and ships on September 15, 2026.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
Changes for add-on developers
Experimental web features
These features are shipping in Firefox 156 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.