Header
Injector
Inject a custom request header into every page you visit — simple key/value pairs you can flip on and off, one at a time or all at once.
Built on Manifest V3 and declarativeNetRequest, so headers hit the real network layer — no interception scripts, and it works on everything from page loads to websockets.
three fields, that's the whole thing
Type a header name and a value. That's a rule — it starts sending on your next page load.
Flip each header on or off on its own, or hit the master switch to bypass everything at once.
Leave a header global, or restrict it to matching sites with * wildcard URL patterns.
what's under the hood
Headers are applied by Chrome's own network layer via declarativeNetRequest — page loads, fetch/XHR, images, even websockets. No per-request scripts, no overhead.
Send a header only where it belongs. Scope by patterns like *://*.example.com/*, comma-separated, with a blank field meaning every site.
Annotate each header with a note, so a wall of tokens still tells you which environment is which at a glance.
Back up your whole setup as JSON and restore it anywhere — the importer also reads ModHeader profile exports, comments and all.
Headers live in Chrome sync storage, so they follow your profile across machines. A badge on the toolbar icon shows how many are live right now.
Malformed header names are flagged in red and skipped rather than quietly breaking the rest of your rules.
Get the extension
Install it free from the Chrome Web Store, or read the source and build it yourself from GitHub.