Thunderbird add-on for checking grammar using LanguageTool.
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Thunderbird Grammar Checker

Thunderbird add-on for checking grammar using LanguageTool.

Official Thunderbird Grammar Checker add-on:

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).

Quick Start

The add-on uses either a local LanguageTool server (recommended) or the public one. Please note that the public server has the certain restrictions: Public HTTP API.

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-3.9
$ java -cp languagetool-server.jar org.languagetool.server.HTTPServer --port 8081


In general, please follow the Thunderbird extensions official documentations. There are several Gradle tasks specified to make the development easier:

  • Run ESLint check for the JS files: gradle eslint
  • Run unit-tests: gradle test
  • Build the XPI file for the deployment: gradle build