# Introduction to Add-on Development

**URL:** <https://discourse.mozilla.org/t/introduction-to-add-on-development/608>\
**Category:** Development\
**Created:** [July 11, 2014, 9:00pm UTC](https://discourse.mozilla.org/t/introduction-to-add-on-development/608 "2014-07-11T21:00:34Z")\
**Posts on this page:** 1\
**Showing post:** 27

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**Author:** ![jorgev](https://avatars.discourse-cdn.com/v4/letter/j/71c47a/32.png) [@jorgev](https://discourse.mozilla.org/u/jorgev)\
**Post date:** [May 27, 2016, 6:10pm UTC](https://discourse.mozilla.org/t/introduction-to-add-on-development/608/27 "2016-05-27T18:10:30Z")

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> [@musiquegraeme](#):
>
> My biggest problem is that I am developing an addon that my company needs for Thunderbird and you’d almost think that Thunderbird doesn’t exist. Everything is about Firefox and there are NO examples of Thunderbird addons.

That’s accurate. The level of support Mozilla gives Thunderbird has varied along the years and traditionally hasn’t been great. All add-on documentation and support is handled by a small group of contributors who work really hard on keeping the project alive. I don’t expect this situation to improve in the future, to be frank.

> [@musiquegraeme](#):
>
> when will XUL be depreciated for Thunderbird?

For Firefox, XUL extensions are planned to be dropped by the end of 2017, and dropping XUL entirely is just a proposal that could take years to complete. For Thunderbird such changes might never happen. To drop XUL extensions there would need to be support for the new API (WebExtensions) in Thunderbird, and I know of no plans to do this.

> [@musiquegraeme](#):
>
> When will addons for Thunderbird need to be signed.

As far as I know, extension signing won’t be a requirement for Thunderbird.

I suggest you give the [Thunderbird planning list](https://mail.mozilla.org/listinfo/tb-planning) a look. You may find the answers to your other questions, or get answers directly from the people in charge.

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