Grammar Guardian

AI-powered grammar correction and writing suggestions using your own LLM API key.

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.