LanguageTool

LanguageTool is the grammar checker for everyone Grammarly leaves out — which is to say, anyone who writes in a language other than English. Developed in Germany (by LanguageTooler GmbH in Potsdam) on an open-source core dating back to 2003, it checks grammar, spelling, punctuation, and style in more than 30 languages, with especially strong coverage of German, French, Spanish, Dutch, Portuguese, and Polish. It even handles regional variants: Swiss German versus Austrian versus standard German, or British versus American English.

The open-source foundation is a genuine differentiator. Privacy-sensitive organizations — law firms, hospitals, government offices, especially in Europe — can run the entire checker on their own servers so no text ever leaves the building. Everyone else uses the cloud service through browser extensions for Chrome and Firefox, add-ins for Word and Google Docs, desktop apps, and a developer API. LibreOffice has shipped with LanguageTool support for years.

For everyday errors, the free tier is genuinely usable rather than a teaser: no account needed, most grammar and spelling rules included. Premium unlocks the deeper layer — advanced style and “Picky Mode” rules, an AI paraphrasing tool, longer text checks, and a team admin console.

Key Features

• Grammar, spelling, and punctuation checking in 30+ languages and regional variants
• Picky Mode for stricter style rules — wordiness, passive voice, formality
• AI-powered paraphrasing and sentence rewriting (Premium)
• Browser extensions, Word and Google Docs add-ins, and desktop apps
• Personal dictionary and team style-guide rules
• Self-hostable open-source server for full data control
• Developer API for embedding checks into other products

Pricing

• Free: core checking with a per-check limit of about 10,000 characters, no signup required
• Premium: roughly $5–8/month on annual billing (more month-to-month), raising limits and unlocking advanced style rules and paraphrasing
• Teams: per-seat pricing with centralized billing and shared dictionaries

Best For

Multilingual writers and teams — a German professional writing English emails and German reports gets one tool for both. Also developers needing a grammar API, and organizations with strict data-residency rules that want to self-host.

Limitations

If you write only in English, Grammarly’s suggestions are more polished and it adds tone detection and clarity rewrites LanguageTool lacks. The free character cap means long documents must be checked in chunks, and the writing-improvement features stop at sentence level — there’s no full-document restructuring help.