Single purpose
Header Relay only captures and relays headers. Requestly's mocking, redirects, and script injection have no equivalent here — and nothing to configure or misconfigure for them either.
Chrome extension comparison
Looking for a narrower Requestly alternative, just for headers?
Requestly is an open-source HTTP interceptor trusted by 300,000+ developers, covering header modification, API mocking, URL redirects, response overrides, and script injection in one extension. Header Relay covers a single slice of that: capturing selected response headers and relaying fixed or captured values to matching requests. If headers are the only piece you use, a narrower tool means fewer permissions and less surface area to review.
What's actually different.
This isn't a safety complaint — Requestly is open source and widely used. It's a scope trade-off: one tool that does everything, or one tool that does one thing.
Small, reviewable code path
Header lifecycle logic lives in one module built entirely on Chrome's declarativeNetRequest API and local storage.
Captured values stay visible
Captured header values are shown in plain text in the popup and management screen, not hidden behind an abstraction.
No account, no cloud sync
Profiles and captured values stay in local Chrome storage. There's nothing to sign into.
If headers are all you use Requestly for, switching is three steps.
Header Relay doesn't import another extension's rules — recreating a header-only setup is quick.
Create a profile
Add the target origins your header rules applied to.
Move over fixed headers
Static values like API keys or client IDs become Fixed Headers.
Automate captured values
Anything you extract from a response — a session token, a trace ID — becomes a Captured Header, reattached automatically.
Questions about switching from Requestly.
Is Requestly unsafe?
No — this page isn't reporting any issue with Requestly. It's open source and widely used. The comparison here is purely about scope: Header Relay does one narrower job.
What am I giving up?
API mocking, response body overrides, URL redirects, and script injection — Header Relay doesn't do any of that. If you rely on those, Requestly remains the better fit.
Can I run both at once?
Generally yes. Header Relay only touches headers for origins in its enabled profile; conflicts are only possible if both extensions target the same header on the same request.
Sources
Header Relay is not affiliated with Requestly or its developers. Feature descriptions above reflect Requestly's public documentation, GitHub repository, and Chrome Web Store listing as of July 2026.