Hi everyone,
a quick heads-up about an upcoming change in the Thunderbird ecosystem that will affect NC Connector users. Mozilla will officially announce this in the coming days – I want to make sure the NC Connector community has the information early.
What's changing
Starting with Thunderbird 153, Mozilla will limit support for the extended Experiment API to the ESR channel (technically via a locked preference in the Release channel).
Since NC Connector currently relies on the Experiment API for parts of its calendar integration, this means: running NC Connector on the regular Release channel of Thunderbird 153+ will not be possible.
What this means for users
The recommended path is to switch to Thunderbird ESR 153 when it ships. ESR is Mozilla's long-term support channel, with a longer maintenance cycle and fewer breaking changes – so this is actually a more stable foundation for productive use, not a downgrade.
For users who want to stay on a more current Thunderbird stream, the Beta channel is an alternative – the Experiment API remains available there.
Timeline
- Soon: Mozilla's official announcement
- Mid-2026: Thunderbird 153 ships as Release, slightly later as ESR
- Until then: No action needed – current versions keep working as before
What we're doing on our side
I'm actively working – including through upstream contributions to Thunderbird – to remove NC Connector's dependency on the Experiment API. The current focus is on the calendar interface, which is one of the last remaining building blocks in this area. Once that work is done, NC Connector will run on all Thunderbird channels again, without requiring ESR.
Questions?
Feel free to comment below if anything is unclear or if you need help planning the transition for your setup.
Cheers,
Bastian
Hi everyone,
a quick heads-up about an upcoming change in the Thunderbird ecosystem that will affect NC Connector users. Mozilla will officially announce this in the coming days – I want to make sure the NC Connector community has the information early.
What's changing
Starting with Thunderbird 153, Mozilla will limit support for the extended Experiment API to the ESR channel (technically via a locked preference in the Release channel).
Since NC Connector currently relies on the Experiment API for parts of its calendar integration, this means: running NC Connector on the regular Release channel of Thunderbird 153+ will not be possible.
What this means for users
The recommended path is to switch to Thunderbird ESR 153 when it ships. ESR is Mozilla's long-term support channel, with a longer maintenance cycle and fewer breaking changes – so this is actually a more stable foundation for productive use, not a downgrade.
For users who want to stay on a more current Thunderbird stream, the Beta channel is an alternative – the Experiment API remains available there.
Timeline
What we're doing on our side
I'm actively working – including through upstream contributions to Thunderbird – to remove NC Connector's dependency on the Experiment API. The current focus is on the calendar interface, which is one of the last remaining building blocks in this area. Once that work is done, NC Connector will run on all Thunderbird channels again, without requiring ESR.
Questions?
Feel free to comment below if anything is unclear or if you need help planning the transition for your setup.
Cheers,
Bastian