Thunderbird Grammar Checker add-on

Official Thunderbird Grammar Checker add-on:

Back-end functionality is based on LanguageTool functionality (in particular, the add-on uses its webserver). Though it can work without any further customization, it is strongly recommended to setup a local LT server (see below), and change the add-on preferences to use your server. By default, the add-on uses the local server and falls back to public LT server (that can't handle the high load and can't guarantee the privacy).
The grammar checking is available via Tools menu, the context menu and the corresponding toolbar button.

Language and server settings can be changed using the add-on preferences:

Supported languages: English (en), Dutch (nl), French (fr), German (de), Italian (it), Polish (pl), Romanian (ro), Russian (ru), Slovak (sk), Slovenian (sl), Spanish (es), Swedish (sv), Ukrainian (uk), Asturian (ast), Belarusian (be), Breton (br), Catalan (ca), Chinese (zh), Danish (da), Esperanto (eo), Galician (gl), Greek (el), Japanese (ja), Khmer (km), Persian (fa), Portuguese (pt), Tagalog (tl), Tamil (ta).

Setting up the local LT server

To use the local server, please download the stand-alone version for the desktop, unpack and run it as described here: HTTP Server.

The sample instructions:

$ wget
$ unzip
$ cd LanguageTool-3.7
$ java -cp languagetool-server.jar org.languagetool.server.HTTPServer --port 8081


Source code is available in Github:


  1. The add-on works for me. However I had problems with the new Firefox 4. I had to go back to the previous FireFox 3.8

    You could also check out they offer a similar engine but with NLP (Natural Language Processing) technology built-in.


  2. EnglishSoftware solution doesn't work in Linux, so it's useless for me.

  3. So I have to switch to thunderbird for email (Long story) and I am one who can not live without grammar checking. how on earth can i get this working on a windows box?

  4. I have personal server (Debian), without X11.
    Is it possible to use it at LanguageTool server, and how to configure it with only command line ?


    1. JRE requires X-server, so probably you won't be able to install LT server. I can only recommend to use the external server, if local unavailable, like this:

  5. This comment has been removed by the author.

  6. Alexander,
    I was really hoping to be able to use this software but it seems to be broken/nonfunctional. Do you have plans to fix it?

    1. Thanks for letting me know, I'll take a look. Apparently, Thunderbird internals have changed, and the extension gives the JS error. Unfortunately, I can't actively maintain the extension, but can fix the major errors like this.

    2. Maintenance version 0.7 having the compatibility with the latest Thunderbird API and LanguageTool API has been released. The source code has been moved to Github, it may help with the issue tracking and pull requests if anyone willing to improve the add-on.

  7. I understand and appreciate that. I have a couple of packages in this status myself.


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