modreq - Modify HTTP Headers

modreq is a free Chrome extension to modify HTTP request headers and cookies — a simple ModHeader alternative for developers and QA. Replace or append request headers on matching traffic. Override cookie values on the site in your active tab. Toggle rules on or off instantly. Everything stays local in your browser — no account, no cloud sync, no tracking. Features: • Replace or append HTTP request headers (Authorization, X-Forwarded-For, custom headers, and more) • Override cookies on the current site without DevTools gymnastics • Enable/disable each rule with one click • Lightweight MV3 extension — rules apply via declarativeNetRequest Use cases: • Test APIs with custom Authorization or feature-flag headers • Debug CORS / proxy scenarios with X-Forwarded-For • Swap session cookies between environments • Quickly A/B header values while browsing Privacy: all rules are stored locally. modreq does not collect or send your data.