From Wikipedia, the free encyclopedia
Developer(s)Daniel Naber and Marcin Miłkowski
Initial release15 August 2005; 18 years ago (2005-08-15)
Stable release
6.2[1] Edit this on Wikidata / 2 July 2023; 28 March 2024
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] The LanguageTool website connects to a proprietary sister project called LanguageTool Premium (formerly 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 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 Premium 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.

LanguageTool does not check a sentence for grammatical correctness, but whether it contains typical errors. Therefore, it is easy to invent ungrammatical sentences that LanguageTool will still accept. Error detection succeeds with a variety of rules based on XML or written in Java.[8] XML-based rules can be created using an online form.[9]

More recent developments rely on large n-gram libraries that offer suggestions for improving misspellings with the help of artificial neural networks.[10]

See also[edit]


  1. ^ "Release 6.2". 2 July 2023. Retrieved 8 July 2023.
  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). Daniel 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. ^ "Linux Administration", Pro Oracle Database 10g RAC on Linux, Berkeley, CA: Apress, pp. 385–400, 2006, doi:10.1007/978-1-4302-0214-1_15, ISBN 978-1-59059-524-4, retrieved 2022-02-23
  9. ^ "Create a new LanguageTool rule". Retrieved 2023-10-26.
  10. ^ SKILL 2018 : Fachwissenschaftlicher Informatik-Kongress, Studierendenkonferenz Informatik, 26.-27. September 2018, Berlin. Gesellschaft für Informatik. [Bonn]. 2018. ISBN 978-3-88579-448-6. OCLC 1066024545.{{cite book}}: CS1 maint: location missing publisher (link) CS1 maint: others (link)

External links[edit]