Firefox ESR
Release Notes

Release Notes tell you what’s new in Firefox. As always, we welcome your feedback. You can also file a bug in Bugzilla or see the system requirements of this release.

140.3.1 Firefox ESR

September 23, 2025

Version 140.3.1, first offered to ESR channel users on September 23, 2025

Firefox 140 Extended Support Release (ESR) includes all of the enhancements since Firefox 128, along with many new features to make your enterprise deployments easier and even more flexible.

Fixed

  • Improved reliability when HTTP/3 connections fail: Firefox no longer forces HTTP/2 during fallback, allowing the server to choose the protocol and preventing stalls on some sites. (Bug 1980812)

Developer

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