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LanguageTool Logo (2018).svg
LanguageTool WikiCheck.png
LanguageTool WikiCheck
Developer(s)Daniel Naber and Marcin Miłkowski
Initial release15 August 2005; 16 years ago (2005-08-15)
Stable release5.2 (19 December 2020; 13 months ago (2020-12-19)) [±][1]
Written inJava
PlatformJava SE
  • Desktop app: 156 MB[2]
  • n-gram data: 8.34 GB[3]
TypeGrammar checker
LicenseGNU LGPL v2.1+ Edit this on Wikidata

LanguageTool is a free and open-source grammar, style, and spell 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.

It 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 each language.[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, LibreOffice, Apache OpenOffice, Vim, Emacs, Firefox, Thunderbird, and Google Chrome. Its web app client can also be integrated on websites.[8]

See also[edit]

External links[edit]

Official website


  1. ^ "LanguageTool Change Log". 19 December 2020.
  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. ^ "Integration On Websites – LanguageTool Wiki". 2014-04-15. Retrieved 2014-05-03.