Firefox 144 for developers
This article provides information about the changes in Firefox 144 that affect developers. Firefox 144 is the current Nightly version of Firefox and ships on October 14, 2025.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
Changes for add-on developers
- Adds the ability to determine the priority of CSS injected from the
"content_scripts"manifest key, inscripting.registerContentScripts()with thecssOriginproperty onscripting.RegisteredContentScript, and thecssOriginproperty incontentScripts.register. By default, the"author"origin takes precedence. (Firefox bug 1679997)
Experimental web features
These features are shipping in Firefox 144 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.