Free AI Grammar Checker Software in 2026

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.

📜 Table of Contents

• The short answer
• Self-host with Docker
• LanguageTool vs Grammarly
• Real numbers
• FAQ

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

docker run -d -p 8010:8010 --name lt --restart always erikvl87/languagetool

Then point any client at http://localhost:8010/v2/check:

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

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.

❓ FAQ

Is the free version enough?

For grammar and spelling - yes. AI-powered sentence rewriting requires the premium tier (or use an LLM yourself).

Can I use it with VS Code?

Yes - the LanguageTool LSP extension works in VS Code, Neovim and other editors.

Does it check Chinese?

Yes, Chinese is among the 25+ supported languages, though the rule depth is strongest for English and European languages.