Modify HTTP request and response headers

ModHeader is a free browser extension for editing HTTP request and response headers. No sign-up. Install it, change a header, and test without touching your app code.

Add to Chrome — It's free

Used by 800,000+ people

Available on:

How it works

Install the extension

Get ModHeader from the Chrome, Firefox, or Edge store. It is free and does not need an account.

Add or modify headers

Open the popup and set request headers, response headers, cookies, and related rules.

Toggle and debug

Turn rules on or off with one click. URL, tab, and resource filters keep changes limited to what you want.

Features

Edit request and response headers

Change request headers, response headers, Cookie, and Set-Cookie from the popup. Set Authorization, flip feature flags, or rewrite X-Forwarded-For without changing app code.

Toggle rules with one click

Enable or disable modifications while you test. Useful when you need the same page with a feature on in one pass and off in the next.

Filter by URL, tab, or resource

Apply rules only on matching URLs, tabs, windows, or resource types so tokens do not leak to other sites.

Edit individual cookies

Rewrite Cookie request headers and Set-Cookie response headers, including attributes, without changing server code.

Build and test CSP headers

Draft Content-Security-Policy response headers in the extension, try them on a page, then copy the result into production config.

Multiple profiles

Keep separate profiles for projects or environments, switch between them, and export or import profiles when you need to share setup with teammates.

Install ModHeader

Free on Chrome, Firefox, and Edge. No sign-up.

Add to Chrome — It's free

FAQs

How do I modify a request header?

Click the ModHeader icon to open the popup. Enter the header name (for example Authorization) and its value, then leave the rule enabled. Matching requests pick it up right away.

Can I limit modifications to certain URLs or tabs?

Yes. URL, tab, window, and resource type filters limit where rules apply, which helps keep tokens off sites you did not mean to touch.

Is ModHeader free? Which browsers are supported?

Yes. ModHeader is free. There is no sign-up, no account, and no paid plan. It runs on Chrome, Firefox, and Edge on Windows, macOS, and Linux.

Does ModHeader collect or sell my data?

No. ModHeader does not collect personal data or browsing history. Profiles and settings stay in local extension storage on your device. See the Privacy Policy for details.