Grammar Guardian

Grammar Guardian uses AI to check your grammar, fix spelling mistakes, and suggest better phrasing — right inside any text field on any website. Bring your own API key from Anthropic (Claude), OpenAI, Google Gemini, or OpenRouter (which offers free models).

HOW IT WORKS
• Focus any text field on any website — a small check button appears
• Click it to send your text for grammar checking
• Review corrections with clear before/after comparisons and explanations
• Apply fixes with one click, or copy the corrected text to clipboard
• Right-click selected text anywhere to check grammar via context menu

SUPPORTED PROVIDERS
• OpenRouter — recommended, offers free models like Gemini Flash and DeepSeek at zero cost
• Anthropic — Claude Haiku, Sonnet, and Opus
• OpenAI — GPT-4o, GPT-4o-mini, GPT-3.5 Turbo
• Google Gemini — Gemini 2.0 Flash, Gemini 1.5 Pro
• Type any custom model ID for OpenRouter (hundreds of models available)

FEATURES
• Inline grammar check button on every text field (textarea, input, contentEditable)
• Detailed change explanations — see why each correction was made
• Style suggestions — optional improvements beyond grammar fixes
• Configurable writing tone — neutral, formal, casual, concise, or creative
• Custom instructions — add rules like "Use British English" or "Keep technical jargon"
• Works with React, Vue, Angular, and other framework-based inputs
• Right-click context menu for checking selected text anywhere
• Quick-check text area in the extension popup

PRIVACY & SECURITY
• Your API key stays in local Chrome storage — never sent to any server except the provider you choose
• No data collection, no analytics, no tracking
• No account required — just your own API key
• All API calls happen in an isolated background service worker
• Fully open source

GETTING STARTED
1. Install the extension
2. Click the Grammar Guardian icon → "Settings & API Key Configuration"
3. Choose a provider and enter your API key (get a free OpenRouter key at openrouter.ai/keys)
4. Start typing in any text field — the check button appears automatically

COST
• Completely free with OpenRouter free models (openrouter/free)
• Paid providers cost ~$0.0001–0.001 per grammar check depending on text length and model

Perfect for writers, students, professionals, non-native English speakers, and anyone who wants polished writing everywhere on the web.