CORS Doctor

Offline CORS error analyzer — diagnoses cross-origin issues with actionable fixes

CORS Doctor is a powerful, fully offline DevTools extension that instantly analyzes and explains CORS (Cross-Origin Resource Sharing) errors directly inside your browser. Instead of wasting time searching for vague error messages like “No ‘Access-Control-Allow-Origin’ header present,” CORS Doctor inspects failed network requests, evaluates request and response headers using a deterministic rule engine, and clearly identifies the exact root cause. It provides accurate explanations along with copy-ready fixes for popular backend frameworks with Java, Python, JavaScript Backends and Nginx as well. With zero AI, no cloud calls, and no data tracking, the extension works entirely on your machine—making it secure, fast, and enterprise-friendly. Designed for frontend developers, backend engineers, and DevOps teams, CORS Doctor helps you diagnose, understand, and fix CORS issues in seconds instead of minutes.