Masthead.
Masthead is a ModHeader alternative for Chrome and Edge: add, change and remove HTTP request and response headers, per site, from a small popup. It never makes a network request.
Coming to the Chrome Web Store and Microsoft Edge Add-ons.
What it does
- Request and response headers. Set a header, or leave the value empty to remove it. Add a comment to each one.
- Profiles. Keep a set of headers for each job (staging, a test user, a feature flag) and switch with a click or Alt+Shift+1 to 3.
- Site filters. Limit a profile to domains or URL patterns, or keep it off some sites.
- Site profiles. Mark a profile for its own sites and it stays on there, next to whichever profile is active, from the very first page load.
- Side panel. Open Masthead in the browser's side panel and it stays open while you click around the page, switch tabs and reload.
- Import from ModHeader or Requestly. Pick your export file, see exactly what comes across and what doesn't, then import. Anything that can't be imported safely is listed, and a profile whose site limits can't all be imported comes in switched off rather than running everywhere.
- Redirects and one-tab profiles with a license: send a production script to your local build, or try headers in one tab without touching the others.
Why trust it with your headers
It never makes a network request. No account, no analytics, no telemetry, no sync, no license server. Your profiles and your license key stay in your browser on your computer. You can check this yourself: open chrome://extensions (edge://extensions in Edge), turn on Developer mode, click Masthead's "service worker" link and watch its Network tab while you use Masthead; for the popup, right-click it and choose Inspect. Nothing appears in either.
It asks for one site at a time. Masthead installs with no access to any site. When you add a site filter, the browser asks you to allow that site, and you can take it back in Settings at any time.
What you install is what runs. Plain JavaScript, no build step, no minified code and no dependencies, so the extension's files are readable as they are.
Price
Free
- Request and response headers
- Unlimited profiles, with site filters
- Site profiles, side panel and keyboard shortcuts
- ModHeader and Requestly import, export
License
- Everything in Free
- Redirect rules
- Profiles scoped to a single tab
Available at launch.
Team of up to five people: $49 once.
One-time purchase, no subscription. Checkout is run by Polar, our merchant of record, which handles payment and sales tax. Your license key arrives by email and is checked offline, inside the extension. Not right for you? A full refund within 30 days, no questions asked.
How it compares
| Feature | Masthead | Requestly |
|---|---|---|
| Account needed | No | Yes |
| Rules on the free plan | No limit of ours (Chrome allows 5,000) | 5 rules, 3 active at once |
| Paid plan | $19 once | From $8 a month (billed $90 a year) |
Requestly figures from its pricing page and sign-up, checked October 13, 2026. Requestly does more than Masthead (mock APIs, sessions, team workspaces); Masthead does headers, filters and redirects, and nothing leaves your browser.
Questions
What happened to ModHeader?
ModHeader was removed from the Chrome Web Store on July 10, 2026. If you still have its export file, or can export from a copy you have installed, Masthead imports it. If ModHeader returns, your Masthead profiles stay yours: export them any time.
Does it work in Microsoft Edge?
Yes. Masthead is one extension for Chrome and Edge (version 121 or later).
Why does the browser ask about a site when I add a filter?
Masthead can only change headers on sites you allow. Asking per site, at the moment you add it, keeps the install free of any "read and change all your data" warning.
Is the license a subscription?
No. You pay once. The key is a signed code checked inside the extension, so it keeps working without ever contacting us.
Who makes it?
Humswoop LLC, a small software company in Independence, Missouri. Questions go to a real person at [email protected].