API Studio

Intercept, inspect, and modify HTTP traffic with Chrome DevTools Protocol.

API Studio is a developer tool for testing websites and web apps by intercepting Fetch/XHR API traffic in the current browser tab. With API Studio, you can create rules that match requests by URL and HTTP method, then modify how those requests behave. You can replace response bodies, change status codes, delay responses, block requests, or transform JSON responses for testing different frontend states. The extension also includes a Studio view where you can inspect intercepted requests, discover API calls, and quickly create rules from real traffic. API Studio is designed for frontend developers, QA engineers, and API testers who need to simulate loading states, error responses, empty states, mock data, and backend edge cases without changing application code or backend services. Core features: Enable or disable interception for the current tab Match requests by URL and HTTP method Replace API response bodies Modify JSON responses Return custom status codes Add artificial response delays Block matching requests Discover API requests and create rules from real traffic Store rules locally in the browser API Studio only runs when you enable interception for a tab. Rules and logs are stored locally in your browser using Chrome extension storage.