OpenGrammar is a free, privacy-first browser extension that gives you Grammarly-like writing help everywhere (Gmail, Google Docs, Notion, Reddit, etc.) without sending your data anywhere.
Key points:
• Core engine runs 100% locally in your browser (rule-based detection of passive voice, repetition, long sentences, readability). No internet needed.
• Optional AI power: just paste your own OpenAI/Groq/OpenRouter/Ollama key. You pay only pennies for what you use. Your key never leaves the browser.
• Tone rewriting (Formal, Casual, Professional, etc.) with one right-click.
• Writing stats dashboard (Flesch score, reading time, vocabulary diversity).
• Underlines suggestions in red/yellow/blue — click to apply.
• Fully self-hostable backend (Cloudflare Workers or Vercel, one-command deploy).I built this because I was tired of Grammarly storing everything I write and charging $30/month. Everything is open source (Apache 2.0), no accounts, no telemetry.
Demo video & screenshots coming soon. Right now you can try it in 2 minutes:
1. Clone the repo
2. Load the unpacked extension (chrome://extensions)
3. (Optional) add your API key
GitHub: https://github.com/swadhinbiswas/opengrammar
Would love feedback from writers, developers, and privacy enthusiasts. What grammar rules should I add next? Any features you miss from Grammarly?
(Also happy to take PRs — especially for more local rules!)