strict compatibility mode enabled - add-ons no longer compatible by default

Magnus Melin mkmelin+mozilla at
Tue Apr 10 20:04:48 UTC 2018

Traditionally add-ons have been set to be compatible by default, i.e. 
not needed an action from the add-on author to continue to function when 
Thunderbird does a major version update. It has often been the case in 
recent releases that the add-ons haven't really worked and caused 
strange bug reports.

For Thunderbird 60 it doesn't make sense to keep the compatible by 
default scheme, given the large amount of code changes in core. If the 
add-on hasn't been updated, it very likely will cause problems - and 
that's not in anybody's best interest. We therefore made the 
extensions.strictCompatibility true in bug 1451097, and the change has 
been landed for the latest Thunderbird 60 beta.

There are still things to do to mitigate the effect of this change, for 
instance we need to make sure dictionaries are marked compatible 
(assuming they are).

If you're an add-on author, now is the time to make sure your add-on is 
compatible with Thunderbird 60, scheduled for release shortly after 
2018-05-09. You can download the beta from If your add-on is 
still compatible without any changes, please visit the Mozilla’s Add-ons 
site and mark it compatible. For your add-on(s), click on “Manage Status 
& Versions”, then under “Listed versions”, click the link for a version 
and adjust the versions it is compatible with. If it's not working, you 
may want to check out the code upgrade gu:

Regarding the extensions.strictCompatibility change, please give 
feedback now even if it's after the fact. If there are too many 
problems, we may need to reconsider the decision.

Follow-ups to tb-planning.


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