DevHeader: Custom Headers & Redirect Rules

Modify request/response headers, redirect URLs, and mock API responses by domain. Named profiles for dev, staging, and prod.

DevHeader is a minimal, local extension for web developers. Modify HTTP request and response headers, redirect URLs, and mock API responses, with no broad permissions and no remote calls. HEADERS - Set, append, or remove request and response headers - Scope rules to specific domains, or apply them globally - Toggle individual rules on and off without deleting them REDIRECTS - Rewrite request URLs with substring or regex find/replace - Live preview of the rewrite, with backreference support API MOCKING - Intercept fetch and XHR calls and return the status, body, and headers you define - Match REST requests by URL and GraphQL requests by operation name - Capture a real request in the DevTools panel and click Add to Mocks, or start from scratch - Edit the response as a form or raw JSON - Simulate 500 and 404 responses, or build a UI before the backend exists - Requires Chrome 138+ and the "Allow User Scripts" toggle on the extension's details page. Response delay simulation is not supported. PROFILES - Named profiles for dev, staging, and prod, with one-click switching - Export and import profiles PRIVACY AND SECURITY - No <all_urls> permission at install. Sites are granted one at a time at runtime - No network calls, no analytics, no remote code - Everything is stored locally in chrome.storage.local A safer alternative to ModHeader. Website: https://www.devheader.com Guide to mocking API responses: https://www.devheader.com/mock-api-responses-chrome Privacy policy: https://www.devheader.com/privacy