HeadMod

Inject and modify HTTP request/response headers and cookies.

HeadMod lets you add, change, or remove HTTP request and response headers — and attach cookies — on the sites you choose. It's a small, focused tool for debugging and testing. I built HeadMod for myself, to debug and test things day to day, and I'm sharing it in case it's useful to you too. It's completely free. No ads, no tracking, no analytics, no accounts, no paid tier, and nothing is ever sent anywhere. WHAT IT DOES - Request headers — set a header's value, or leave the value empty to remove the header from outgoing requests. - Response headers — do the same for headers coming back. - Cookies — attach cookies to outgoing requests, or to responses. - Profiles — keep separate sets of rules (staging, local, a specific client) and switch between them in one click. - URL filter — scope a profile to matching URLs, or leave it blank to apply everywhere. - Toggle anything — flip individual rules on and off, or switch the whole extension off with one shortcut. The toolbar badge shows how many rules are currently active. - Undo / redo, light and dark themes, and keyboard shortcuts for everything you do often. PRIVACY HeadMod is built on Chrome's declarativeNetRequest API. That means your rules are handed to Chrome and applied by the browser itself — the extension never intercepts, reads, or sees the contents of your network traffic. It can't, by design. Site access is optional and entirely yours to control. On install, HeadMod has access to nothing. You choose: grant it every site, or grant individual sites one at a time. Rules only ever apply where you've allowed them, and you can revoke access whenever you want. Your rules are stored locally in your browser and never leave your device. FEEDBACK Suggestions, bug reports, and feature ideas are genuinely welcome — this is a tool I use myself, so I'd like it to be good. Reach out any time. LINKS Source code: https://github.com/Lomank123/head-modifier Issues and suggestions: https://github.com/Lomank123/head-modifier/issues AUTHOR Linkedin: https://www.linkedin.com/in/lomank Website: https://lomank.com