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Firefox extension: port to Thunderbird?

Unfortunately the Grammar-checker doesnt work anymore with latest version of TB.

As OP, I think LT needs a plugin for Thunderbird, could it be possible to make the existing Firefox compatible?

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Firefox has changed its way of developing add-ons to WebExtensions, I think this is not compatible with Thunderbird. So a new extension would need to be developed, or the existing extension would need to be updated.

Thanks for your reponse dnaber, sure, how can I help in this way? I really think a standalone TB extension would be amazing.

The best way is probably to download and try to make it work again. As the add-on hasn’t been updated for quite some time, it will still use our old API (which doesn’t work anymore), so you’d need to port it to the new one documented at

If you have questions, let us know here in the forum. We had never offered an official Thunderbird add-on, so I’m not sure if we can help with Thunderbird-specific questions.

Please, please, please,

Could someone work on the Thunderbird add-on?

It would be extremely useful.


Yes and the extension is now outdated and I hope there is an official add-on for thunderbird

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The extension for Firefox installs without difficulty, and preferences can be set:

– however it’s not effective when drafting an e-mail.

yeah, that is too bad and one of the main point for Thunderbird is writing email directly within the app.

Unfortunately, it does not support the version of Thunderbird I have on Ubuntu.

Yes, the unofficial addon for Thunderbird is quite obsolete and I hope new maintainer or new app can help to mitigate the issue

+1 for having a thunderbird addon!
Since Thunderbird should use again the same addon tech as Firefox do, it shouldn’t be to hard to build it on the base of the existing Firefox addon (hopefully!)

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Full aware this is an old old thread but I can’t seem to find the source code for this Add-On. Did anyone have any luck?

I can have a go at getting it working. It would be quite a bonus.

We plan to support Thunderbird soon (for a broader definition of “soon”…), now that it “just” needs to be ported from Firefox.



I toyed with version 4.0.1, for Firefox, in Thunderbird.

Whilst there’s no obvious error when I set it to work with localhost, I get an empty personal dictionary. As if there might be a communication issue.

I look forward to support for Thunderbird …

+1 for Thunderbird support. It’s crucial to have it in one of the most used work communication tool.

We’re still waiting for the review by Thunderbird, but our add-on has been released now at


Mozilla Thunderbird problems sending emails – This issue can occur if your email account isn’t properly configured.

Could you send a screenshot of the problem? Does it only happen with LanguageTool activated?


Very excited to see LanguageTool working in Thunderbird! It works fine for me except one significant problem – I can no longer use the ^x “cut” shortcut to cut text. I use cut and paste all the time to reorganize email messages as I draft them, so this is a serious problem. I am trying to get used to just highlight and drag to move text around, but hopefully you can fix this bug. ^c and ^v for “copy” and “paste” both still work. It is just ^x that is gone. When I disable LT ^x works again, so it must be this plug in. I am using plug in version 4.1.1 and Thunderbird version 78.14.0 on Windows 10.