Firefox 142 for developers
This article provides information about the changes in Firefox 142 that affect developers. Firefox 142 is the current Nightly version of Firefox and ships on August 19, 2025.
Note: The release notes for this Firefox version are still a work in progress.
Changes for web developers
Media, WebRTC, and Web Audio
- The
currentRoundTripTime,totalRoundTripTime, andresponsesReceivedproperties of theRTCIceCandidatePairStatsdictionary are now supported. These return the current round trip time (RTT) and the information needed to calculate the average RTT for the connection. (Firefox bug 1371391).
Changes for add-on developers
- Cookies created with
cookies.set()in Nightly are now validated, and invalid cookies are rejected. The implementation in Nightly is to enable monitoring for any issues. The intention is to enforce validation in all channels in a future release. (Firefox bug 1976197)
Experimental web features
These features are shipping in Firefox 142 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.