HeaderForge: HTTP Header Modifier (ModHeader Alternative)

Open-source alternative to ModHeader — add, modify, and remove HTTP request and response headers with profiles and filters.

HeaderForge is a fast, open-source HTTP header modifier. A ModHeader alternative for developers, QA engineers, and anyone who needs to test HTTP headers without touching server code. Features: • Add, modify, or remove request and response headers (set / append / remove) • Organise rules into colour-coded profiles you can toggle on/off • Scope profiles to specific sites with URL regex filters • Annotate each header with a description • Import/export as JSON; pause everything with one click • Light / dark / system themes with a resizable popup Why HeaderForge? • Open-source — code is on GitHub, no hidden behaviour • Private by design — no accounts, no analytics, no network requests • Manifest V3 — built on declarativeNetRequest for modern Chrome/Edge/Brave • Data stays local — everything is stored in your browser How it works: 1. Click the toolbar icon 2. Add a header name and value on the Request or Response tab 3. The header is applied immediately to matching requests 4. Use URL Filters to limit a profile to specific sites 5. Use the pause button to switch everything off temporarily