Free, open-source grammar checker powered by Claude & OpenAI.
Stop paying $144/year for Grammarly. GrammarPeace gives you the same features — grammar checking, tone rewriting, and translation — using the best AI models available, for free.
Website · Chrome Web Store · Report Bug
| Feature | Grammarly | GrammarPeace |
|---|---|---|
| Price | $144/year | Free |
| AI Model | Proprietary | Claude & OpenAI (state-of-the-art) |
| Data Privacy | Collects your writing | Your data stays yours |
| Open Source | No | Yes |
| Word Limits | Yes | No |
- Grammar Check — Instant grammar and spelling corrections with one-click fixes
- Improve Text — Make your writing sound more natural and native
- Tone Rewriting — Rewrite text as Professional, Casual, Friendly, Formal, or Concise
- Translation — Translate between 15+ languages instantly
- Explain Corrections — Learn why changes were made
- Diff View — See exactly what changed with highlighted differences
- Writing Statistics — Word count, reading time, Flesch readability score
- Quick Presets — Save your favorite language + tone combinations
- History — Access your recent corrections
- Dark Mode — Easy on the eyes
- Works Everywhere — Gmail, Twitter, LinkedIn, any website
- Select text on any webpage
- Click the ✌️ button that appears
- Choose an action: Check, Improve, Tone, or Translate
- Copy or Replace the result with one click
Keyboard shortcut: Ctrl+Shift+G (or Cmd+Shift+G on Mac)
- Download or clone this repository
- Open Chrome →
chrome://extensions/ - Enable Developer mode (top right toggle)
- Click Load unpacked → select this folder
- Done!
GrammarPeace requires an API key from Anthropic or OpenAI:
- Click the extension icon → Settings
- Choose your AI provider:
- Anthropic (Claude): console.anthropic.com
- OpenAI: platform.openai.com
- Paste your API key and save
API Cost: Typical usage costs a few cents per month. Much cheaper than $12/month subscriptions.
GrammarPeace uses the latest AI models for fast, accurate results:
| Provider | Model | Notes |
|---|---|---|
| Anthropic | Claude Haiku 4.5 | Fast, cost-effective, excellent quality |
| OpenAI | GPT-5 Nano | Lightweight and efficient |
You can switch between providers in Settings. Both deliver excellent grammar checking at minimal cost.
Grammarly Premium: $144/year ($12/month)
GrammarPeace: Pay only for what you use
| Provider | Input | Output | Cost per 1000 checks* |
|---|---|---|---|
| Claude Haiku 4.5 | $1.00/M tokens | $5.00/M tokens | ~$0.30 |
| GPT-5 Nano | $0.10/M tokens | $0.40/M tokens | ~$0.025 |
*Estimated based on ~100 input tokens + ~100 output tokens per grammar check.
A heavy user checking 100 texts per day:
- Grammarly: $144/year (fixed)
- Claude Haiku 4.5: ~$11/year
- GPT-5 Nano: ~$0.90/year
That's 13-160x cheaper than Grammarly, with better AI.
English, Spanish, French, German, Italian, Portuguese, Russian, Japanese, Korean, Chinese, Arabic, Hindi, Turkish, Dutch, Polish
GrammarPeace is designed with privacy as a core principle:
- No servers — We don't operate any servers. Zero.
- No accounts — No sign-up, no login, no tracking.
- No data collection — We don't collect analytics, usage stats, or personal data.
- Direct API calls — Your text goes directly from your browser to the AI provider.
- Local storage only — Your API key and settings stay in your browser.
- Open source — Read the code yourself.
grammarpeace/
├── manifest.json # Extension configuration (Manifest V3)
├── background.js # Service worker for API calls
├── content.js # Content script for text selection UI
├── content.css # Styles for the grammar panel
├── popup.html/js # Extension popup
├── options.html/js # Settings page
├── icons/ # Extension icons
└── docs/ # Website files
- Chrome Extension Manifest V3
- Anthropic Claude API / OpenAI API
- Vanilla JavaScript (zero dependencies)
- Pure CSS (no frameworks)
Contributions welcome!
- Found a bug? Open an issue
- Have an idea? Suggest a feature
- Want to help? Submit a pull request
MIT License — use it however you want.
Made with ✌️ by kaansrc
GrammarPeace is not affiliated with Anthropic or OpenAI. It's an independent open-source project.