Modify Header
Control your HTTP headers in one click.
Add, change or remove HTTP request and response headers on any site — no code, no DevTools. Fully open source and privacy-first.
Modify Header
4 active rules
Switching from ModHeader?
In July 2026, Google removed ModHeader from the Chrome Web Store and Microsoft pulled it from Edge after security researchers found hidden code capable of collecting users' browsing data. Modify Header is a fully open-source, privacy-first replacement: every header stays on your machine, nothing is tracked, and nothing is ever sent to a server. Don't take our word for it — read every line of the source yourself.
Everything you need to shape a request
Purpose-built for developers, testers and QA engineers working with APIs and environments.
Add, edit & remove
Set any header on requests or responses, tweak its value, or strip it out entirely.
Request & response
Modify both directions — perfect for testing CORS, auth flows and API behaviour.
One-click toggles
Flip any header rule on or off instantly, without deleting your setup.
Group by profile
Organise rules for staging, production or per-API sets and switch between them.
Private by design
Everything stays in local storage. No external requests, no data ever leaves your browser.
Open source
The full code is public on GitHub — audit it, fork it, or contribute anytime.
Install & start modifying
From zero to your first header rule in under a minute.
Add it to your browser
Install the extension, then pin it to your toolbar for one-click access from any page.
Create a header rule
Open the panel, choose Request or Response, enter a header name and value, and toggle it on.