| LanguageTool | |
|---|---|
  Show dark mode version of fileShow light mode version of file | |
| Developers | Daniel Naber and Marcin Miłkowski |
| Initial release | 15 August 2005 (2005-08-15) |
| Stable release | 6.81 
/ 5 May 2026 |
| Written in | Java |
| Platform | Java SE |
| Size | |
| Type | Grammar checker |
| License | GNU LGPL v2.1+ |
| Website | languagetool |
| Repository | |
LanguageTool is a free and open-source grammar, style, and spell checker, and all its features are available for download.45 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.
Overview
LanguageTool was started by Daniel Naber for his diploma thesis6 in 2003 (then written in Python). It now supports 31 languages, each developed by volunteer maintainers, usually native speakers of each language.7 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,8 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, TeXstudio, Apache OpenOffice, Vim, Emacs, Firefox, Thunderbird, and Google Chrome.5
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.9 XML-based rules can be created using an online form.10
More recent developments rely on large n-gram libraries that offer suggestions for improving misspellings with the help of artificial neural networks.11
In April 2023 Learneo acquired LanguageTool.12131415
References
References
- "Release 6.8". 5 May 2026. Retrieved 7 May 2026.
- "Index of /download/". languagetool.org.
- "Index of /download/ngram-data/". languagetool.org.
- "LanguageTool - Spell and Grammar Checker". LanguageTool.
- Ashwin (2019-07-08). "LanguageTool is a free, open-source, grammar and spell checker - gHacks Tech News". gHacks Technology News. Retrieved 2025-04-23.
- Daniel Naber. "A Rule-Based Style and Grammar Checker" (PDF). Daniel Naber.de. Retrieved 30 June 2018.
- "Supported languages". 28 December 2016. Retrieved 29 December 2016.
- "N-Gram Data Download Page". languagetool.org. 2019-03-30. Retrieved 2019-03-30.
- "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
{{citation}}: CS1 maint: work parameter with ISBN (link) - "Create a new LanguageTool rule". community.languagetool.org. Retrieved 2023-10-26.
- 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) - Naber, Daniel. "LanguageTool joins Learneo".
- "Learneo | Updates | Learneo, Inc. Accelerates AI Writing Innovation with LanguageTool Acquisition". www.learneo.com. Retrieved 2025-04-10.
- Pathak, Shalini (2023-04-10). "US-Based Learneo Acquires Multilingual Writing Assistant LanguageTool – EdTechReview". Retrieved 2025-04-23.
- Alston, Fiona (2023-04-05). "Learneo adds LanguageTool to its stable of AI-powered writing tools and services, in its latest acquisition". Tech.eu. Retrieved 2025-04-23.