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
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.
Light & dark themes
Work in a warm light theme or an easy-on-the-eyes dark mode — your choice is remembered.
Side panel mode
Dock the editor in your browser's side panel and adjust headers while you keep using the page.
Current-tab autofill
One tap fills in the active tab's domain, so new rules target the site you're on instantly.
Import rules in bulk
Load or paste a whole set of header rules at once instead of adding them one by one.
Draft auto-save
Half-finished rules are kept as you type, so nothing is lost if you close the panel.
Master on/off switch
Disable every rule with a single toggle, then flip them all back on when you need them.
See Modify Header in action
A quick walkthrough of adding, editing and toggling header rules on a live site.
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.
Modify Header
Open source · Runs locally · No data collected.