Headrule - Modify HTTP Request & Response Headers

Headrule modifies HTTP request and response headers for any URL, directly inside Chrome. It is built for the everyday jobs of API and frontend developers: sending an Authorization token to a staging API, faking a User-Agent or Referer, toggling a feature-flag header, or adding CORS headers while you develop locally. WHAT IT DOES - Set, append or remove any request or response header - Scope each rule to a domain (||api.example.com), a URL prefix, or a regular expression - Rules apply from the next request, nothing to restart - Profiles for staging, production, client work, CORS debugging - One switch (or Alt+Shift+H) pauses every rule - The toolbar badge shows how many rules are live - Clear error messages when Chrome cannot apply a rule WHY HEADRULE Headrule uses Chrome's declarativeNetRequest API. Your rules are handed to the browser's own request engine, which means no background script reading your traffic, no content scripts, and no way for the extension to see page content. There is no account, no analytics and no remote code. The only network request it ever makes is the license check when you activate Pro. SWITCHING FROM MODHEADER ModHeader was removed from the Chrome and Edge stores in July 2026. Headrule imports ModHeader JSON exports for free: profile names, request and response headers, enabled states, comments and URL filters. A rule whose filter cannot be converted is imported switched off with a note, so nothing is sent where you did not intend. FREE AND PRO Free: unlimited request and response rules, URL filters, one profile, pause switch, import and export (including ModHeader files). Pro ($9, one payment, no subscription): unlimited profiles, regex URL filters, and sync across your Chrome browsers through your own Chrome account. WORKS WITH Chrome, Edge, Brave, Arc and other Chromium browsers. SUPPORT support@headrule.com · Privacy policy: https://headrule.com/privacy.html Headrule is an independent project and is not affiliated with Google or with ModHeader.