HTTP header inspector

Fetch any URL, see every response header, the full redirect chain, and the time it took. Like curl -ILv but rendered nicely.

/tools/headers does a single GET on the URL with all redirects followed manually (capped at 10 hops). The result page shows:

The final HTTP status, colour-coded by class (2xx teal, 3xx purple, 4xx amber, 5xx red).
Total round-trip time in milliseconds.
The redirect chain — every hop with its status and Location target — so you can spot a chain that’s too long or that goes from HTTPS back to HTTP somewhere.
Every response header, alpha-sorted.

Useful for debugging an OG card that won’t render (need to check what content-type Twitter saw), a missing cookie (which Set-Cookie actually came back), or a CDN that’s adding a stale Cache-Control somewhere.