Cool Headers

Cool Headers adds, replaces, and removes HTTP request headers automatically, based on which site you are on. THE PROBLEM IT SOLVES If you already use a header editor, you know the routine: you keep one profile for test, one for staging, one for production — and every time you switch environments you have to remember to switch the profile too. Forget once and you are debugging a "broken" staging API for ten minutes before realizing you were sending your test token. Cool Headers removes that step. You attach each rule to a URL match pattern instead of to a profile. Open test.example.com and the test auth header is already applied. Open staging.example.com and the staging one is. Both rules stay enabled at the same time, because they can never both match. There is nothing to toggle and nothing to remember. HOW IT WORKS 1. Click the toolbar icon and press Add Rule. 2. Give it a URL pattern — press the location button to fill it in from the tab you are on. 3. Add the headers you want set or removed. That is it. From then on, every matching request carries those headers. The toolbar badge shows how many of your rules are active on the current page, and the popup lists them by name, so you always know what is being sent before you start debugging. WHAT YOU CAN DO WITH IT • Keep separate auth tokens or session cookies for every environment, all live at once • Send feature-flag or debug headers to a single service without touching the rest of your traffic • Strip headers a proxy or corporate extension is injecting, with the Remove operation • Add or remove URL query parameters on matching requests, not just headers • Impersonate a different user or role on a staging site, and flip between identities in one click • Point rules at localhost ports and internal hostnames, not just public domains FEATURES • URL-pattern rules — headers apply automatically on matching requests, no switching • Set and Remove header operations • Query parameters — add, replace, or remove params on matching URLs • Rule groups — rules sharing a URL pattern are collected under one header • One at a time — an optional per-group mode where enabling one rule disables its siblings, for cycling through tokens or roles on the same domain • Active rules indicator — a toolbar badge plus an "Active on this page" list, so nothing is applied invisibly • Duplicate — copy a rule in one click; the copy starts disabled so you can edit it safely • Import / export rules as JSON, to back them up or hand a working setup to a teammate • Open in Tab — a resizable full-page view when the popup gets too small for your rule set • Follows your system light or dark theme URL PATTERN EXAMPLES *://test.example.com/* any request to test.example.com *://*.example.com/* any subdomain of example.com, including the bare domain *://localhost:3000/* a local dev server on port 3000 https://api.example.com/* HTTPS only WHO IT IS FOR Web developers, QA engineers, and anyone who works across more than one deployment of the same application and is tired of profile switching being a manual step. PRIVACY Cool Headers has no server, no account, no analytics, and no telemetry. Your rules are stored in your own browser profile through Chrome's storage API — they sync across your own signed-in devices and go nowhere else. The extension makes no network requests of its own, reads no page content, and contains no remote code. It is fully open source, so you can verify all of that yourself. Full privacy policy: https://github.com/okxiaochen/cool-headers/blob/main/PRIVACY.md Source code: https://github.com/okxiaochen/cool-headers