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LanguageTool WikiCheck
LanguageTool WikiCheck
Developer(s)Daniel Naber and Marcin Miłkowski
Initial release15 August 2005; 14 years ago (2005-08-15)
Stable release4.8 (27 December 2019; 24 days ago (2019-12-27)) [±][1]
Repository Edit this at Wikidata
Written inJava
PlatformJava SE
  • Desktop app: 156 MB[2]
  • n-gram data: 8.34 GB[3]
TypeGrammar checker
LicenseGNU LGPL v2.1+

LanguageTool is a free and open-source grammar checker, and all its features are available for download.[4] LanguageTool website connects to a proprietary sister project LanguageTool Plus, which provides improved error detection for English and German, as well as easier revision of longer texts, following the open-core model.

LanguageTool was started by Daniel Naber for his diploma thesis[5] in 2003 (then written in Python). It now supports 31 languages, each developed by volunteer maintainers, usually native speakers of said languages.[6] Based on error detection patterns, rules are created and then tested for a given text.

The core app itself is free and open-source, and can be downloaded for offline use. Some languages use 'n-gram' data,[7] which is massive and requires considerable processing power and I/O speed, for some extra detections. As such, LanguageTool is also offered as a web service that does the processing of 'n-grams' data on the server side. LanguageTool Plus also uses n-grams as part of its freemium business model.

LanguageTool web service can be used via a web interface in a web browser, or via a specialized client-side plug-ins for Microsoft Office,[8] LibreOffice,[9] Apache OpenOffice,[10] Vim,[11][12] Emacs,[13][14] Firefox,[15] Thunderbird,[16] and Google Chrome.[17] Its web app client can also be integrated on websites.[18]

See also[edit]


  1. ^ "LanguageTool Change Log". 27 December 2019.
  2. ^ "Index of /download/".
  3. ^ "Index of /download/ngram-data/".
  4. ^ "LanguageTool - Spell and Grammar Checker". LanguageTool.
  5. ^ Daniel Naber. "A Rule-Based Style and Grammar Checker" (PDF). Retrieved 30 June 2018.
  6. ^ "Supported languages". 28 December 2016. Retrieved 29 December 2016.
  7. ^ "N-Gram Data Download Page". 2019-03-30. Retrieved 2019-03-30.
  8. ^ "LanguageTool Microsoft Office Plug-in". 11 January 2019. Retrieved 29 December 2016.
  9. ^ "LanguageTool v4.4" (OXT). Retrieved 11 January 2019.
  10. ^ "LanguageTool v2.5" (OXT). Retrieved 30 June 2018.
  11. ^ "LanguageTool – Grammar checker for English, French, German (etc.) in Vim : vim online". Retrieved 2014-05-03.
  12. ^ "vim-grammarous: A powerful grammar checker for Vim using LanguageTool". GitHub. Retrieved 2014-09-30.
  13. ^ Schroeder, Alex (2013-08-24). "langtool.el". EmacsWiki. Retrieved 2014-05-03.
  14. ^ Hayashi, Masahiro. "Emacs-langtool". GitHub. Retrieved 2019-03-18.
  15. ^ "Grammar and Spell Checker - LanguageTool". Mozilla Foundation. 2018-12-26. Retrieved 2019-01-05.
  16. ^ "Grammar Checker". Mozilla Corporation. 2013-05-17. Retrieved 2014-05-03.
  17. ^ "LanguageTool - Grammar and Style Checker". Google Chrome Webstore. Google. 2017-12-17. Retrieved 2017-12-29.
  18. ^ "Integration On Websites – LanguageTool Wiki". 2014-04-15. Retrieved 2014-05-03.