Firefox 158 release notes for developers (Beta)
This article provides information about the changes in Firefox 158 that affect developers. Firefox 158 is the current Beta version of Firefox and ships on October 13, 2026.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
Changes for add-on developers
publicSuffix.isKnownSuffix()now throws an error when passed an invalid hostname, instead of returningfalse. (Firefox bug 2066620)- Adds
runtime.getVersion()to return the extension's version as declared in the manifest. (Firefox bug 1992418)
Experimental web features
These features are shipping in Firefox 158 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.