LanguageTool

LanguageTool is a rules-based grammar checker covering 31 languages with full grammar support — the widest multilingual coverage in this category. Its LGPL-2.1 core is self-hostable, which now matters more than it used to: in December 2025 the browser extension moved behind a Premium paywall, making a self-hosted server the only free way to check text outside the web app.

What You Get#

• 31 languages with full grammar rules: Arabic through Ukrainian, including German, French, Spanish, Portuguese, Polish and Chinese. Norwegian is a 32nd language but spellcheck-only.
• Self-hostable open-source core: LGPL-2.1-or-later on GitHub and actively maintained (v6.8, May 2026). Community Docker images run an unlimited private server on your own machine.
• Picky Mode and a personal dictionary: Optional stylistic strictness beyond basic grammar, plus a custom word list so character and place names stop getting flagged.
• Native apps and office plugins: macOS and Windows desktop apps, an iOS app, and add-ins for MS Word, Google Docs and LibreOffice. No first-party Android app.
• AI rephrasing: Sentence-level paraphrasing, 3 per day free and unlimited on Premium.

Who It's For#

• Authors writing outside English: Nothing else in this category comes close on German, French, Spanish, Portuguese or Polish.
• Authors who won't upload an unpublished manuscript: The self-hosted server never sends a word off the machine, and costs nothing.
• Budget-conscious English-language authors: Around $60/yr is the cheapest credible paid grammar tool — but read the extension caveat below first.

Pricing: Free tier is web-checker-only — 2,000 characters per check (~350 words) and 3 AI rephrases per day. Premium is priced in EUR through a geo-keyed checkout: €19.90 monthly, €39.90 quarterly, €59.89 per year (~€4.90/mo), or €99.90 for two years (~€4.16/mo). Teams is €56.90 per user per year up to 20 seats, contact-sales above that. Students and teachers get 20% off with code EDUCATION. 14-day money-back guarantee on all Premium purchases.

Strengths#

• Multilingual depth no competitor matches: ProWritingAid, Grammarly and AutoCrit are English-first. This is the only credible option for a German or Spanish manuscript.
• Genuinely self-hostable: Current releases, working Docker images, no character cap and no subscription on your own server.
• No AI training on your text, by default: A December 2024 terms update stopped customer input being used to train its models, with no opt-in required. Grammarly defaults training on for free and individual Pro accounts.
• Cheapest credible annual price: Roughly $60/yr against Grammarly Pro's $144/yr.

Limitations#

• The browser extension is Premium-only since December 2025: Chrome, Firefox, Edge and Safari extensions now require a subscription — free users get 14 days, then the extension stops working. This was the free tier's headline feature.
• Two different character caps: 150,000 characters (~25,000 words) in the web app and API, but 100,000 per check in the browser extension. Chapter-by-chapter either way, not whole-manuscript.
• No fiction awareness: No pacing, dialogue or genre reports. Like Grammarly, it flags intentional fragments and dialect-heavy dialogue as errors.
• "German company" no longer implies EU data residency: Founded in Potsdam in 2003, but Learneo, Inc. (California) acquired it in April 2023 and is the data controller named in the current terms.

Alternatives#

ProWritingAid is the pick for English-language fiction — manuscript reports and native Scrivener integration LanguageTool has no answer for. Grammarly still ships a free browser extension, now the clearest reason to pick it instead, though it runs $144/yr and defaults AI training on. QuillBot also has a free extension — and LanguageTool's own paywall notice sends displaced users there, since Learneo owns both.