AI Grammar Checker 2026: LanguageTool (15k Stars) - The Free Open Source Alternative to Grammarly
Grammarly Premium costs $12/month and your writing flows through their servers. LanguageTool gives you grammar checking in 30+ languages, open source and self-hostable - here is the honest 2026 comparison.
💡 What You Will Learn
Grammarly Premium costs $12/month and your writing flows through their servers. LanguageTool gives you grammar checking in 30+ languages, open source and self-hostable - here is the honest 2026 compar
📜 Table of Contents
The short answer
LanguageTool (14,757 stars) is the leading open-source grammar checker in 2026: rule-based engine plus AI models, 30+ languages, browser extensions, desktop apps, and a self-hostable server. For privacy-conscious writers and non-English speakers, it beats Grammarly on coverage and price.
What LanguageTool offers
- 30+ languages: real grammar checking in German, French, Spanish, Chinese, and more - not just English.
- Rule-based + AI: traditional language rules catch what LLMs miss (style consistency, punctuation), while their AI adds context-aware rephrasing.
- Everywhere: browser extensions (Chrome, Firefox, Edge), Word/Google Docs add-in, desktop app, and a REST API.
- Self-hostable: the community server runs on your own infrastructure - your text never leaves your network.
- Free tier is genuinely useful: grammar and spelling corrections are free; style suggestions need Premium.
Quick start (self-host)
docker run --rm -p 8081:8081 --name languagetool -e langtool_languageModel=/ngrams erosmariandri/languagetool
# then POST text to http://localhost:8081/v2/check
Or just install the browser extension and use the free public server.
Grammarly vs LanguageTool (2026)
| Aspect | LanguageTool | Grammarly |
|---|---|---|
| Price | Free / Premium $4.99-7.49 | Free / $12/mo |
| Languages | 30+ | English only |
| Privacy | Self-host option | Cloud only |
| Open source | Yes | No |
FAQ
Is the free version enough? For grammar and spelling: yes. Style and tone suggestions need Premium, but the free tier covers most everyday writing.
How accurate is it? Very good on grammar rules; comparable to Grammarly on common errors, better on non-English text.
Can I use it with sensitive documents? Self-host the server and your text never leaves your machine.
Related
❓ FAQ
Is the free version enough?
For grammar and spelling: yes. Style and tone suggestions need Premium, but the free tier covers most everyday writing.
How accurate is it?
Very good on grammar rules; comparable to Grammarly on common errors, better on non-English text.
Can I use it with sensitive documents?
Self-host the server and your text never leaves your machine.
Written by our editorial team; tools listed here are tested or verified against public sources. Links point to official sites or GitHub repos for reference only โ no paid placements.
