Updating Add-Ons for Thunderbird 78

John Bieling john at thunderbird.net
Sat Aug 22 19:33:29 UTC 2020

I would like to share an alternative strategy to update add-ons for Thunderbird 78. This information has already been send to many of our add-on developers.Since this topic was also discussed in tb-planning, it seems useful to 
share this information here as well.

Migrating an existing legacy add-on to a MailExtension can be a time-consuming process: MailExtensions use different APIs than legacy add-ons and no longer have direct access to all parts of Thunderbird. To support add-on developers, we created two wrapper APIs (Experiments) to get add-ons compatible with Thunderbird 78 without going through the whole porting process. The idea behind this is to make add-ons compatible with the current ESR as quickly and easily as possible, so users can continue to work with their beloved add-ons. The actual conversion to pure MailExtensions then takes place in smaller steps, for which I - the Thunderbird add-on support engineer - will develop small tutorials, whereby the legacy parts will be removed step by step.

These wrapper APIs are explained in detail in our addon-developer-support repository:

We can provide further support through our add-on developer mailing list and our chat rooms:


More information about the tb-planning mailing list