Header Sets

Define sets of HTTP request headers and activate one set at a time while browsing.

Header Sets lets you define named groups of HTTP headers and activate one group at a time while you browse. Built for developers who juggle environments: staging auth tokens, API keys, locale overrides, CORS testing. ★ Sets, not single headers — group the headers that belong together ("Staging auth", "QA locale") and switch with one click ★ Scope each set to specific sites with a URL filter (*.myapp.dev, localhost, https://api.example.com/v1/*) so tokens never leak elsewhere ★ Request AND response headers — set, append, or remove either direction (e.g. add Access-Control-Allow-Origin: * for CORS testing) ★ Toggle individual headers on/off to compare behavior ★ Export/import sets as JSON to share configs with your team ★ Toolbar badge shows which set is active; invalid or sensitive header names are flagged as you type ★ Follows your OS light/dark theme Built on Chrome's declarativeNetRequest API: headers are applied by the browser's rule engine, with no JavaScript intercepting your traffic and no performance overhead. Privacy: everything stays in your browser. No accounts, no analytics, no remote servers — see the privacy policy.