LanguageTool

LanguageTool is a free and open-source proofreading tool that checks grammar, style, punctuation, and spelling. It supports more than 20 languages and provides contextual suggestions to improve writing quality. The software uses language-specific rule sets to identify potential errors and stylistic issues.

Users can run LanguageTool as a stand-alone desktop application or as a server that can be queried via an API. It also offers browser extensions for Chrome and Firefox, and add-ons for word processors such as LibreOffice and OpenOffice, as well as integrations with Google Docs. The spell-check component commonly relies on Hunspell dictionaries, while grammar and style checks are driven by a rule-based engine.

LanguageTool was initiated by Daniel Naber in the early 2000s and is developed by a volunteer community. It is distributed under a free software license, with optional commercial hosting services that provide additional features and capacity. The project maintains documentation and source code on its official website and on GitHub.

Because language coverage and rule quality vary across languages, the tool may produce false positives or miss certain errors. It is intended as an aid to writing rather than a substitute for professional proofreading. LanguageTool is widely used by individuals, educators, and organizations for multilingual text checking.