Header Injector

Header Injector adds, overrides or removes HTTP request and response headers on the sites you choose. It is built for admins and developers who need to reproduce or troubleshoot header-dependent behavior, such as tenant restrictions, debug flags, API versioning or security headers, without setting up a proxy. Features • Multiple rules, each with its own list of URL patterns and headers • Wildcard URL patterns: bare domains (example.com covers all subdomains), *.example.com, https://*.example.com/api/*, localhost:3000, or * for every URL • Set or remove request headers; set, append or remove response headers • On/off switches for the whole extension, each rule, and each header • Toolbar popup for quick toggling, with per-tab hit counts showing which rules actually modified requests • Problems such as invalid header names or malformed patterns are flagged inline How it works Rules are applied by Chrome's built-in declarativeNetRequest engine. The extension never reads page content or request bodies, and all configuration stays in local extension storage on your device. Nothing is sent anywhere.