Checking a caching header
https://example.com
200 OK, plus a Cache-Control header explaining how long a CDN or browser may keep this response.
HTTP Header Checker
See any public URL's status code and response headers, with short explanations for the cache and security ones.
Response
The result will appear here.
We fetch the target from our server on your behalf — the address you enter isn't stored.
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About this tool
Response headers carry information a browser acts on silently: how long to cache a page, whether it may be framed, which script sources it trusts. Reading them for a URL you don't control — a competitor's site, a CDN-fronted asset, your own production server from outside its network — needs a request a browser's own dev tools can't make across origins, which is why this fetches the target from our server instead.
How to use it
- Enter any public URL — the scheme defaults to https if you leave it off.
- Press Check to fetch it and see its status code, response time and every header it returned.
- Headers that affect caching or security get a one-line explanation of what they actually do.
Examples
Common problems
- The check fails with a private-network error.
- The target resolves to a loopback, private or link-local address (including cloud metadata endpoints) — this check only reaches the public internet, by design, so it can't be used to probe internal infrastructure.