Since exactly which version does TB support WebExtensions?

[pstover]

Since exactly which version does TB support WebExtensions (instead of old AddOns)?

[morat]

The developers are still working on the implementation of various web extension APIs.

Add support for WebExtensions
http://bugzilla.mozilla.org/show_bug.cgi?id=1396172

WebExtensions buglist
http://bugzilla.mozilla.org/buglist.cgi ... ions%20API

Docs for WebExtension APIs
http://bugzilla.mozilla.org/show_bug.cgi?id=1503501
http://thunderbird-webextensions.readth ... en/latest/
http://developer.mozilla.org/docs/Mozil ... hunderbird

For reading only as Bugzilla is not a forum.

[tanstaafl]

Support for legacy add-ons is supposed to be retained (though some code changes will be required) as gradually more WebExtension APIs are added. There is no time table yet for when a useful stable set of WebExtensions for mail will be available. Things are being adopted piecemeal, many of them browser-centric. They keep talking about "WebExperiments" (add-on authors implement an experimental WebExtension API in their add-on, generalize it, propose it be included in Thunderbird, other developers review and modify it, and then it eventually gets included in Thunderbird). Its not clear when the first WebExperiment will be stable enough its safe to rely upon it being available (either via the add-on or in Thunderbird).

https://github.com/thundernest/sample-extensions

[tanstaafl]

A related discussion is at Find out if a *.xpi is an (old) AddOn or (new) WebExtension?