new addons: xul, bootstrapped, webextensions, what to use

Philipp Kewisch kewisch at
Sun Sep 2 22:27:25 UTC 2018

On 9/2/18 3:32 PM, opto at wrote:
> Maybe someone can summarise the current status of what is best to use for new addons in:
> a) TB 60
> b) future TB.
> I think I noticed that bootstrapped addons can be fully debugged within TB, which would speak to use them over xul.
> But some time ago, I read in this forum the intention/necessity to make bootstrapped obsolete, just as xul (because following FF code?).
> So there is for me a lot of confusion of what to use.
> Also, is it worthwhile to adopt abandoned addons and try to get them running in TB 60, or is that 'wasted' time because their technology (most likely xul) will vanish anyway? If so, in which technology to rewrite their functionality?
> How long will TB 60 persist?
> thanks,
> Klaus
> _______________________________________________
> tb-planning mailing list
> tb-planning at

Thunderbird 60 will persist until Thunderbird 60.9.0, which is set to
release some time around October 2019 and coincides with the Thunderbird
68.1.0 release.

Using XUL add-ons is not recommended. bootstrapped add-ons will exist
until about Thunderbird 65. What you should look into is WebExtension
Experiments, and devising Thunderbird-specific APIs around that.
Unfortunately Thunderbird 60 is missing some of the more important basic
WebExtension features, but I hope to backport this in an upcoming minor
release. They work fairly well in nightly though.

You can read more about WebExtension Experiments in Thunderbird here: 

If you would like an intermediate path, you could aim for a bootstrapped
add-on. Note however you will need to rewrite to a WebExtension at some
point before Thunderbird 68. Upgrading from a bootstrapped add-on to a
WebExtension could be less effort than doing so from a XUL add-on, but
my recommendation would still be to write it as a WebExtension Experiment.

I'm sure this brings up a lot of questions I'd love to answer, and more
importantly document so that others can benefit. It would be great if
you could help us identify where we need to improve our documentation.


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