Proofly is a free, open-source Chrome extension that brings professional-grade writing assistance directly to your browser—without compromising your privacy. Unlike cloud-based alternatives like Grammarly, LanguageTool, or QuillBot, Proofly uses Chrome's Built-in AI APIs to proofread your writing entirely on-device. Your keystrokes never leave your machine.

Traditional writing assistants require sending your text to remote servers:

• ❌ Your private data travels across the internet
• ❌ Your writing is stored on company servers
• ❌ Requires constant internet connectivity
• ❌ Subject to data breaches and privacy violations
• ❌ Injects excessive UI to the sites you visit
• ❌ Expensive subscription fees

Proofly runs 100% locally on your device:

• ✅ Zero data transmission - Everything stays on your machine
• ✅ Complete privacy - No servers, no logs, no tracking
• ✅ Works offline - No internet required after model download
• ✅ Free forever - Open source, no subscriptions
• ✅ Lightweight - Minimal script injection, zero dependencies
• ✅ User friendly - Introduces fresh, non-invasive UX patterns
• ✅ Customizable - Complete control on how you'd like to get assistance

• On-Device Processing: All AI proofreading happens locally using Chrome's Built-in AI models
• Zero Server Communication: Your text never leaves your browser
• No Telemetry: We don't collect any usage data or analytics
• Open Source: Complete transparency - audit the code yourself

• Multilingual: Supports all languages that the built-in Gemini Nano model provides
• Spelling Corrections: Catch typos and misspellings instantly
• Grammar Fixes: Subject-verb agreement, tense consistency, and more
• Punctuation: Proper comma usage, missing periods, quotation marks
• Capitalization: Sentence starts, proper nouns, title case
• Preposition Usage: Correct preposition selection
• Missing Words: Detect incomplete sentences

• Visual Highlights: Color-coded underlines for different issue types
• Inline Corrections: Click any highlight to see suggestions
• Keyboard Shortcuts: Quick access with customizable hotkeys (Cmd/Ctrl+Shift+P)
• Auto-Correct Mode: Real-time checking as you type
• Manual Mode: Check on-demand whenever you want
• Selection Correction: Proofread your own highlighted text on-demand
• Issues Sidebar: View issues, navigate through them and apply suggested corrections in a dedicated panel
• Undo/Redo Support: Full history management for corrections

• Lightweight: Minimal footprint (<5KB initial injection)
• Fast: Instant suggestions powered by local on-device AI
• Shadow DOM Isolation: No interference with host pages
• Works Everywhere: Input fields, textareas, contenteditable elements
• Web Standards Compliant: Ignores auto-correction on fields based on their semantics

• Configurable Correction Types: Enable/disable specific issue types
• Custom Colors: Personalize highlight colors for each issue type
• Underline Styles: Choose solid, wavy, or dotted underlines
• Keyboard Shortcuts: Customize your workflow with auto-fix or manual-fix options
• Autofix on Double-Click: Quick correction with double-click

1. Privacy You Can Verify: Open-source code means no hidden data collection
2. No Subscription Treadmill: Free forever, no artificial limitations
3. True Offline Mode: Works on airplanes, remote locations, anywhere
4. Lightning Fast: No network latency, instant corrections
5. Resource Efficient: Minimal CPU and memory usage
6. Non-Invasive: Minimal native code is injected to the sites only when needed
7. No Account Required: No sign-up, no email, no personal info
8. Future-Proof: Uses Chrome's standard Built-in AI API and modern web tech

Proofly is built with modern web technologies and best practices:

• TypeScript - Strict type safety, comprehensive type coverage
• Web Components - Custom components - no framework bloat
• Chrome Built-in AI API - On-device proofreading and language detection models

• Web Components - Standards-compliant custom elements with Shadow DOM
• Vanilla JavaScript and CSS - Zero framework dependencies for minimal bundle size
• Functional Programming - Pure functions, composition, immutability
• Dependency Injection - Testable, modular service architecture
• Event-Driven Communication - Loosely coupled components

• Shadow DOM - Complete style isolation, no CSS conflicts
• CSS Custom Properties - Design token system for theming
• CSS Highlights API - Native browser highlighting for performance
• Popover API - Native popup positioning and management

• Chrome Storage API - Sync settings across devices
• Chrome Side Panel API - Dedicated sidebar interface
• Chrome Context Menus API - Right-click integration
• Content Scripts - Page interaction and highlighting
• Service Workers - Background processing

• TypeScript Compiler - Type checking and transpilation
• Vite Plugin Ecosystem - Build optimization and bundling
• Chrome Web Store Packaging - Automated release builds
• Hot Module Replacement - Instant dev feedback

• Operating System: Windows 10/11, macOS 13+, Linux, or ChromeOS (Chromebook Plus)
• Chrome Version: Chrome 141+
• Storage: At least 22 GB free space (for AI model download)
• GPU: Recommended 4+ GB VRAM for optimal performance
• Network: Internet connection for initial model download (one-time)

Proofly requires Chrome 141 or later with the Built-in AI Proofreader API enabled.

Note: The Proofreader API is in origin trial and will be available in stable Chrome soon.

1. Visit the Chrome Web Store listing
2. Click "Add to Chrome"
3. Follow the on-screen setup

1. Download the latest release from GitHub
2. Extract the ZIP file
3. Open Chrome and navigate to chrome://extensions/
4. Enable "Developer mode" (toggle in top-right)
5. Click "Load unpacked"
6. Select the extracted dist/ folder
7. Click on the Proofly icon and follow the setup wizard

# Clone the repository
git clone https://github.com/onderceylan/proofly.git
cd proofly
# Install dependencies
npm install
# Start development server with hot reload
npm run dev
# Build for production
# The extension will be built to dist/
npm run build
# Load dist/ as an unpacked extension in chrome://extensions/ for testing the prod build
# Load dev/ as an unpacked extension in chrome://extensions/ for testing the HMR dev build

• Node.js 18+ and npm
• Chrome Canary or Chrome Dev
• Git

# Install dependencies
npm install
# Start development server (auto-rebuilds on changes)
npm run dev
# Build the project
npm run build
# Type checking
npm run typecheck
# Linting
npm run lint
# Format checking and fixing
npm run format:check
npm run format
# Unit tests
npm run test
npm run test:watch
# Puppeteer tests
npm run test:e2e
npm run test:e2e:watch
# For setting up e2e test env, load extension in Chrome once for your test-focused puppeteer user profile
# 1. Download https://www.google.com/chrome/dev/
# 2. Run `npm run test:e2e:watch` to open the browser profile of puppeteer or launch the browser manually with `/Applications/Google\ Chrome\ Dev.app/Contents/MacOS/Google\ Chrome\ Dev \ --user-data-dir=$HOME/.cache/chrome-devtools-mcp/chrome-profile-canary --load-extension=./projects/proofly/dev --no-first-run --hide-crash-restore-bubble`
# 3. Open chrome://extensions/
# 4. Enable "Developer mode"
# 5. Click "Load unpacked"
# 6. Select the dev folder
# 7. Download the AI model once

See AGENTS.md for comprehensive development guidelines, including:

• Architecture principles
• Code style conventions
• Testing workflows
• Chrome extension patterns
• Logging guidelines

We welcome contributions from the community! Whether you're fixing bugs, adding features, or improving documentation, your help is appreciated.

1. Pick an Issue: Browse open issues or propose new features
2. Fork & Branch: Create a feature branch from main
3. Make Changes: Follow our coding standards and conventions
4. Test Thoroughly: Verify your changes work as expected through automated e2e tests
5. Submit PR: Open a pull request with a clear description

• Privacy First: No data collection, no tracking, no telemetry
• Minimal Footprint: Keep bundle sizes small
• Long-term Maintenance: Avoid dependencies, and keep building on native web standards
• Non-Invasive: Respect the user's page and experience, keep injections minimal and isolated
• Accessibility: Support all users, including those with disabilities
• Performance: Optimize for speed and efficiency

1. Zero Data Collection: We don't collect, store, or transmit any user data
2. On-Device Processing: All AI runs locally on your machine
3. No Analytics: No telemetry, no usage tracking, no crash reports
4. No Accounts: No sign-up, no user profiles, no personal information
5. Open Source: Fully auditable codebase for transparency

• Minimal Permissions: Only requests essential Chrome APIs
• Content Security Policy: Strict CSP prevents code injection
• Shadow DOM Isolation: UI components that are injected to the sites are completely isolated
• No External Resources: All assets bundled with extension
• Regular Security Audits: Community-driven code reviews

Read our full Privacy Policy for more details.

This project is licensed under the MIT License - see the LICENSE file for details.

• Chrome Team - For developing the Built-in AI API and making on-device AI accessible
• Open Source Community - For the amazing tools and libraries that make this possible
• Contributors - Everyone who helps improve Proofly
• Users - For trusting us with your privacy and writing

• Documentation: AGENTS.md
• Privacy Policy: PRIVACY.md
• Chrome Built-in AI: developer.chrome.com/docs/ai/built-in-apis
• Issue Tracker: GitHub Issues
• Discussions: GitHub Discussions

• Bug Reports: Open an issue
• Feature Requests: Request a feature
• Questions: Start a discussion

If you find Proofly useful, please consider:

• ⭐ Starring the repo
• 🐛 Reporting bugs
• 💡 Suggesting features
• 🔀 Contributing code
• 📢 Spreading the word

Privacy-first writing assistance is possible. Let's prove it together.