API.Guru – API Interceptor & Mock

API Mock & Error Injector is an essential developer tool built for web developers, QA engineers, and test automation specialists. Effortlessly intercept network traffic, inject custom API error statuses, simulate network latencies, and mock endpoint payloads directly in your browser without altering backend code. Key Features Live Network Interception: Dynamically intercept HTTP requests on your active browser tab using Google Chrome Manifest V3. Real-Time API Failure Alerts: Receive native Chrome desktop notifications automatically whenever an intercepted request returns an error status ($\ge 400$). Custom Mocking Rules: Override response bodies, modify status codes (400, 401, 404, 500), and inject network delay to test edge cases. Instant Toggle Control: Enable or disable interceptor rules with a single click right from the extension popup. Dark Mode UI: Modern, lightweight popup UI styled with intuitive status indicators and crisp vector iconography. How to Use Open the API Mock & Error Injector popup from your Chrome toolbar. Configure your custom mocking rules and HTTP status codes. Toggle Enable Interceptor on. Test your frontend UI against simulated network conditions and monitor real-time failure alerts.