Open-source alternatives to Grammarly for grammar and writing
This hub lists open-source grammar checking and writing tools people compare with Grammarly-style AI writing assistants. Grammarly is named only to identify that class of product.
No verified options listed yet.
How we pick
- Actively maintained with recent releases (2024-2026) or established stable projects.
- License copied from the repository LICENSE file.
- Grammar checking, style linting, or writing assistance features.
- No quality ranking; we have no sourced comparison against Grammarly.
Comparison
| Name | License | Stars (GitHub) | Best for |
|---|
Listed open-source writing tools: LanguageTool (LGPL-2.1, multilingual grammar checker), Vale (MIT, style linter for developers), Gramformer (MIT, neural grammar correction), and humanizer (Apache-2.0 12B local rewriter; 2,182 Hugging Face likes as of 2026-10-28). Local rewrite is a different job from rule-based grammar: start at Undetectable.ai alternatives. For AI chat writing, see ChatGPT alternatives. For office suites, see Microsoft Word alternatives.
Why people look for Grammarly alternatives
Grammarly is a popular AI-powered writing assistant with grammar, spelling, style, and tone suggestions. People search for alternatives because:
- Open-source preference: Want tools they can audit, modify, and self-host
- Privacy: Prefer not to send text to cloud services
- Cost: Grammarly Premium and Business tiers are subscription-based
- Offline work: Need tools that work without internet
- Customization: Want to write custom grammar rules or style guides
- Technical writing: Need linting for docs-as-code and Markdown
Writing tool categories
Open-source Grammarly alternatives fall into patterns:
- Grammar checkers: LanguageTool is a full-featured proofreading tool
- Style linters: Vale enforces style guides (Microsoft, Google, AP, custom)
- Neural correctors: Gramformer uses transformer models for grammar fixes
- AI models: Humanizer is a language model for rewriting and style changes
We do not claim any matches Grammarly’s proprietary AI, tone detection, or plagiarism checker.
Listed tools: quick comparison
| Tool | Type | License | Best for |
|---|---|---|---|
| LanguageTool | Server/app | LGPL-2.1 | Grammar, spelling, 30+ languages, self-hosted |
| Vale | CLI linter | MIT | Style guides, docs-as-code, CI/CD, Markdown |
| Gramformer | Python lib | MIT | Neural grammar correction, programmatic use |
| humanizer | LLM | Apache-2.0 | Local style/readability rewrite (not detector advice) |
All stats are verified from official repositories as of 2026-10-16 checks, or marked unverified.
Listed options
FAQ
What is the best open-source Grammarly alternative?
It depends on your needs. LanguageTool (LGPL-2.1) is the most mature multilingual grammar checker, Vale (MIT) focuses on style guides for technical writing, and Gramformer uses transformer models for grammar correction. We do not claim any matches Grammarly's AI suggestions or tone detection.
Do these tools check grammar as well as Grammarly?
LanguageTool is feature-rich with thousands of rules and supports 30+ languages. Vale is more about style consistency than grammar. Gramformer uses neural models. None match Grammarly's proprietary AI models, but LanguageTool is production-ready for many use cases.
Can I self-host these tools?
Yes. LanguageTool offers a Java server for self-hosting. Vale runs locally as a CLI tool. Gramformer is a Python library you can integrate. Check each project's docs for deployment options.
Do they work with Microsoft Word or Google Docs?
LanguageTool has browser extensions and integrations for LibreOffice, Word (via add-in), Google Docs, and more. Vale is CLI-based for code editors and CI/CD. Gramformer is a library for programmatic use. Integration coverage varies.
Are language models available for grammar?
Yes. The Humanizer model is listed here for AI-based grammar/style transformation. See the [Humanizer model page](/models/humanizer/) for details on how to run it.
Sources & verification
- https://github.com/languagetool-org/languagetool
- https://github.com/errata-ai/vale
- https://github.com/PrithivirajDamodaran/Gramformer
- https://huggingface.co/jialinyyzz/humanizer
License notes are not legal advice. Read the original LICENSE. Trademark & disclaimer.