Open-source multilingual grammar and style checker supporting 30+ languages
LanguageTool is an open-source grammar, style, and spell checker supporting over 30 languages with the same depth of analysis it provides for English. Its browser extension, LibreOffice plugin, API, and self-hosted deployment options make it the most versatile multilingual writing tool — the definitive choice for non-English writers, privacy-conscious teams, and developers building grammar checking into applications.
LanguageTool is a strong fit if its core strengths match your workflow, budget, and support needs. Use the quick signals below before opening the full review.
LanguageTool's founding in 2003 predates most grammar checking tools, and its two-decade development history shows in the depth of its language support. Where Grammarly treats non-English languages as secondary features, LanguageTool was built with linguistic parity as a core principle — its German, French, and Spanish grammar engines are maintained by native-language linguists and reflect genuine grammatical depth.
LanguageTool supports over 30 languages, but the depth varies meaningfully. Its highest-quality language support includes English, German, French, Spanish, Portuguese (both Brazilian and European), Dutch, Polish, and Catalan — languages with active rule development and maintenance. For a German speaker writing professional business German, LanguageTool catches complex grammatical errors (case agreement, verb placement in subordinate clauses, Komma rules) that English-first tools cannot approach.
LanguageTool's LGPL-licensed core can be downloaded and run on private infrastructure. Organisations with data privacy requirements — medical, legal, financial, government — can run grammar checking locally without any text leaving their network. The self-hosted server accepts text via a REST API identical to LanguageTool's public API, enabling seamless transition between cloud and self-hosted deployment without application changes.
LanguageTool's public API provides grammar checking programmatically — useful for CMS integrations, Slack bots, custom writing tools, and any application where grammar checking should be embedded rather than delegated to a browser extension. The free tier allows 20 requests per minute; Premium API access raises limits significantly. For developers building writing improvement features, LanguageTool's API is the most accessible and well-documented grammar checking service available.
Score: 8.7/10 — Best multilingual grammar checker and best for privacy-conscious self-hosted deployment; English-only users may prefer Grammarly's style suggestions.
Free
Free billed annually
LanguageTool is best for Writers and professionals working in languages other than English who need a native-language-quality grammar checker, European businesses and teams writing professionally in German, French, Spanish, or other EU languages, Privacy-conscious organisations that need grammar checking without sending text to third-party cloud services.
Yes. LanguageTool currently lists a free plan in ToolRankr data.
It has a free plan.
LanguageTool is reviewed using ToolRankr's scoring model for ease of use, value, features, support, and overall quality. Affiliate links may earn a commission, but sponsored labels do not change editorial scoring.
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