Open-source grammar and style checker covering more than 30 languages
LanguageTool is a grammar, spelling and style checker with an unusual origin for this category: it is open source, and the core engine can be downloaded and self-hosted. It checks more than thirty languages and goes beyond spelling to flag grammar slips, punctuation, confused words and repetition, with rule sets that vary by dialect. You can use it in the browser, as a desktop app, or through extensions for Chrome, Firefox, Word, Google Docs and Outlook. The free tier covers a useful amount of text per request; premium tiers raise the limits. Self-hosting is the differentiator, letting organisations keep text on their own infrastructure.
Last updated: 2026-09-20. This site only provides an index; for exact features, pricing, and licensing, see the official website.
multilingual proofreading, academic writing, business email and self-hosted deployments
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The core grammar engine is published under the LGPL and can be downloaded and self-hosted, which is unusual in this category. Parts of the commercial service, including some premium rule sets and the hosted cloud infrastructure, are not open.
More than thirty, including English, German, French, Spanish, Portuguese, Dutch and Polish. Rule coverage differs by language: English and German are the most developed, while a few languages have much smaller rule sets.
LanguageTool leans toward grammar and multilingual coverage and can run on your own servers. Grammarly concentrates on polished English style advice and integrates deeply into browsers and office apps, but it is closed and cloud-only.
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