The likely future of Thunderbird Addon architecture

R Kent James kent at
Fri Dec 16 18:09:58 UTC 2016

On the thread "DownThemAll and WebExtensions [... or why I am    done
with mozilla]" we have this comment from Andrew Swan <aswan at>:

"We have no intention of
stranding users who want to use extensions to explore the world of chrome
privileged code.  You'll still be able to use bootstrapped extensions
(which run privileged code) locally using dev edition or nighty."

That means to me that it should be straightforward to continue
supporting bootstrapped extensions for the foreseeable future, assuming
that we continue as a binary application on the Gecko codebase as is our
default plan. Continuing extension support for XUL overlays would be
much more problematic. This is also still pretty fuzzy, as XUL overlays
are also integral to the current UI for Thunderbird and I presume also
Firefox, so like XPCOM it is hard to see those going away soon. Yet I
can clearly see that code to support XUL overlays as extensions could be
removed from Gecko relatively soon.

Let me be so bold as to say that the 3 year plan for Thunderbird
extensions is likely to be support for bootstrapped extensions (which
also work today) while eventually XUL-based extensions will have to be


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