API Response Interceptor

Developer tool for API testing - intercept and mock API responses, add delays, with in-page toast notifications and rule templates

API Response Interceptor is a powerful developer tool that helps web developers test, debug, and mock API responses without modifying backend code. Key Features - Response Modification - Replace entire response bodies with custom JSON Modify specific JSON fields using JSON path notation Use regex find & replace for text transformations Header Management -Add, modify, or remove response headers Test CORS configurations Simulate different server behaviors Status Code Control -Override HTTP status codes Test error handling in your applications Simulate server errors for edge case testing Developer-Friendly -Intuitive rule-based system with groups for organization URL pattern matching with wildcards and regex support Import/Export rules for team sharing Real-time network request monitoring Use Cases -API Mocking - Mock API responses during frontend development before the backend is ready -Error Testing - Simulate error responses to test error handling -Edge Case Testing - Test how your app handles unusual response data -Demo Preparation - Prepare consistent demo data for presentations -Legacy System Testing - Test integrations with systems you can't modify How It Works Create rules with URL patterns to match specific API endpoints Define how responses should be modified Attach the debugger to a tab Browse normally - matching responses are automatically modified Privacy & Security All data is stored locally on your device No external servers or analytics No data collection whatsoever Open source and transparent