LanguageTool explained

LanguageTool is a free and open-source grammar, style, and spell checker, and all its features are available for download.^{[1] [2]} 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 thesis^[3] in 2003 (then written in Python). It now supports 31 languages, each developed by volunteer maintainers, usually native speakers of each language.^[4] 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,^[5] 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.

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. XML-based rules can be created using an online form.^[6]

More recent developments rely on large n-gram libraries that offer suggestions for improving misspellings with the help of artificial neural networks.^[7]

In April 2023 Learneo acquired LanguageTool.^{[8] [9] [10] [11]}

See also

• Autocorrection
• Grammarly
• Natural language processing

Notes and References

1. Web site: LanguageTool - Spell and Grammar Checker. LanguageTool.
2. Web site: Ashwin . 2019-07-08 . LanguageTool is a free, open-source, grammar and spell checker - gHacks Tech News . 2025-04-23 . gHacks Technology News . en-US.
3. Web site: A Rule-Based Style and Grammar Checker. Daniel Naber. Daniel Naber.de. 30 June 2018.
4. Web site: Supported languages. 28 December 2016. 29 December 2016.
5. Web site: N-Gram Data Download Page . languagetool.org . 2019-03-30 . 2019-03-30.
6. Web site: Create a new LanguageTool rule . 2023-10-26 . community.languagetool.org.
7. Book: SKILL 2018 : Fachwissenschaftlicher Informatik-Kongress, Studierendenkonferenz Informatik, 26.-27. September 2018, Berlin. 2018. Gesellschaft für Informatik. 978-3-88579-448-6. [Bonn]. 1066024545.
8. Web site: Naber . Daniel . LanguageTool joins Learneo .
9. Web site: Learneo Updates Learneo, Inc. Accelerates AI Writing Innovation with LanguageTool Acquisition . 2025-04-10 . www.learneo.com . en.
10. Web site: Pathak . Shalini . 2023-04-10 . US-Based Learneo Acquires Multilingual Writing Assistant LanguageTool – EdTechReview . 2025-04-23 . en-US.
11. Web site: Alston . Fiona . 2023-04-05 . Learneo adds LanguageTool to its stable of AI-powered writing tools and services, in its latest acquisition . 2025-04-23 . Tech.eu . en-GB.