HeaderMod

HeaderMod - Inject, update, edit, modify, override HTTP headers

A lightweight and open source browser extension that lets you intercept outgoing HTTP requests and inject, update, edit, modify, or override headers on a per-URL basis.

Key Features

• Define multiple header-modification rules
• Wildcard-based URL matching (e.g., .example.com/)
• Add or replace any request header (name + value)
• Enable or disable rules individually
• Persist rules in local storage for seamless browser restarts
• Dynamic toolbar icon indicates active rules

1. Click the HeaderMod toolbar icon to open the popup.
2. Click Add Rule to create a new entry, then fill in:
   • Header-Name and Header-Value
   • Optional URL Pattern (supports * wildcards)
   • Optional Notes for your reference
   • Enabled checkbox to toggle the rule
3. Modify or delete rules as needed.

• Browse your sites as usual
• Each enabled rule is tested against the request URL
• Matching requests have their headers updated or appended before they leave the browser

• HeaderMod does not collect, transmit, or share any personal data. All settings remain in your browser’s local storage and are never sent to any external server.