Firefox and Thunderbird hit the fortnightly release treadmill
Mozilla has released Firefox 155 and Thunderbird 155 as both projects switch to a fortnightly release schedule, meaning updates will now land roughly every two weeks rather than the previous slower cadence. Mozilla announced the accelerated pace for Firefox in July, with MZLA subsequently confirming Thunderbird would follow suit; users who dislike frequent updates are advised to move to the Extended Support Release (ESR) rather than disabling automatic updates altogether.
Firefox 155's headline changes are mostly AI-related, including a wider rollout of the "Smart Window" feature and improved LLM-assisted tab-group naming, alongside a new (though not yet widely available) tracker-blocking counter in the address bar, reorderable browser containers, faster page loading via Happy Eyeballs v3, better game-controller navigation, and larger PDF print scaling. An "AI kill switch" introduced in Firefox 148 remains available for those who want to disable such features, while this release adds local translation support for Marathi and Urdu. Thunderbird 155 focuses on more practical additions, including new policy controls for its QR code sync-export feature and experimental settings, a default address book option, improved S/MIME encrypted attachment handling, and various OAuth authentication enhancements.
In short
- Firefox and Thunderbird move to fortnightly release cycles from September
- Firefox 155 adds AI features plus Marathi and Urdu translation support
- Thunderbird 155 improves QR sync controls, S/MIME handling and OAuth
Steelman: both sides, in good faith
The strongest fair case each way — we don't pick a winner.
The case for
A fortnightly cadence can deliver security fixes and useful improvements sooner, while giving Mozilla a regular way to respond to changing web standards and user needs. The AI features are optional or controllable, and the ESR remains an alternative for people and organisations who value a slower, more predictable update cycle.
The case against
Frequent releases can mean more disruption, repeated interface changes and less time for users or administrators to assess updates before they arrive. Even with an ESR option, maintaining separate release paths may add complexity, and a faster cadence risks making headline features feel like a stream of incremental changes rather than substantial improvements.
Explained simply
Mozilla is the organisation behind Firefox, a web browser, and Thunderbird, an email application. Both projects have traditionally released updates less often than every two weeks, giving users time between new versions.
A release schedule affects how often users receive new features, fixes and security updates. People who prefer fewer changes can use an Extended Support Release, or ESR, which receives updates on a slower schedule. Firefox and Thunderbird also serve different needs: Firefox is used to browse websites, while Thunderbird manages email and calendars.