Free AI Grammar Checker Software in 2026: LanguageTool (14k Stars) Self-Hosted vs Grammarly - Private Writing Assistant

LanguageTool (14,768 stars, LGPL-2.1) is the open-source Grammarly alternative: grammar, style and tone checks in 25+ languages, self-hostable so your writing never leaves your server.

💡 What You Will Learn

LanguageTool (14,768 stars, LGPL-2.1) is the open-source Grammarly alternative: grammar, style and tone checks in 25+ languages, self-hostable so your writing never leaves your server.

## The short answer **LanguageTool** (14,768 stars, LGPL-2.1) is the leading open-source writing assistant. It checks grammar, spelling, style and tone in 25+ languages, integrates with Word, browser extensions, and editors, and - crucially - can be self-hosted for complete privacy. ## Self-host with Docker ```bash docker run -d -p 8010:8010 --name lt --restart always erikvl87/languagetool ``` Then point any client at `http://localhost:8010/v2/check`: ```bash curl -d "language=en-US" -d "text=This sentence have a error." http://localhost:8010/v2/check ``` The API returns each match with replacements, context, and rule details. ## LanguageTool vs Grammarly | Feature | LanguageTool | Grammarly | |:--------|:------------:|:---------:| | Price | Free / self-hosted | Freemium, paid tier | | Languages | 25+ | English only | | Privacy | Full control (self-host) | Cloud processing | | AI rewrites | Premium (paid) | Premium | | Integration | Browser, Word, editors | Browser, apps | ## Real numbers - The free LanguageTool web version checks up to 20,000 characters per text. - The server edition handles thousands of checks per hour on a 2GB VPS. - German, French, Spanish and Chinese all have mature rule sets - Chinese is supported alongside English. ## FAQ **Q: Is the free version enough?** A: For grammar and spelling - yes. AI-powered sentence rewriting requires the premium tier (or use an LLM yourself). **Q: Can I use it with VS Code?** A: Yes - the LanguageTool LSP extension works in VS Code, Neovim and other editors. **Q: Does it check Chinese?** A: Yes, Chinese is among the 25+ supported languages, though the rule depth is strongest for English and European languages.