What is Header Override?
Header Override is an open-source browser extension for Chrome, Edge, and Firefox that lets developers modify HTTP request and response headers and cookies directly from the browser. It is built for scoped debugging, API testing, staging checks, and QA workflows.
Key Features
- Header editor — Add request headers, response headers, request cookies, and response cookies in focused tabs.
- URL scoping — Match rules with browser-supported URL filter patterns so changes apply only where intended.
- Cookie control — Set response cookie Domain, Path, SameSite, Lifetime, Max-Age, and Secure attributes.
- Local profiles — Keep up to five rule profiles for different projects, accounts, or test setups.
- Import and export — Move selected profiles between browsers using local JSON files.
- Rule management — Enable, disable, delete, and annotate rules with comments.
- Cross-browser support — Works in Chrome, Edge, and Firefox.
Privacy by Design
Rules are stored locally in browser extension storage and are never sent to a server. There are no analytics, no tracking, and no external servers. Request values are sent only to matching destinations, and response values are applied only to matching responses.
Common Uses
- Send debug headers to staging APIs without changing application code.
- Reproduce customer-specific headers or cookies with scoped local rules.
- Toggle backend flags while testing UI flows.
- Switch between client, environment, or test-account setups with profiles.
- Document temporary QA rules before removing them.
Header Override is a lightweight, open-source alternative to ModHeader for local header and cookie overrides.