HTTP Headers Checker

Fetches the full set of HTTP request and response headers for any URL, showing exactly what the server sends back before any browser rendering or JavaScript execution touches it. This is the ground-truth view for debugging caching behavior, redirect chains, content negotiation, cookie flags, or CDN behavior, since browser dev tools sometimes show headers after they've been modified client-side. Response headers alone often explain browser behavior that otherwise looks unexplainable.

Common things to check first: Cache-Control and ETag explain why a page won't update after a deploy; Set-Cookie flags (Secure, HttpOnly, SameSite) explain login/session bugs across subdomains; a Vary header that doesn't match your CDN's cache key is a frequent cause of one visitor seeing another visitor's cached page. If a header you expect is missing entirely, check whether a reverse proxy or CDN in front of your origin is stripping it.

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