HTTP Header Checker

What it does

This tool grades the HTTP response headers that matter most for SEO and basic security. You paste the output of curl -I, and it reads the status line and eight headers: X-Robots-Tag, Content-Type, Cache-Control, Content-Encoding, Strict-Transport-Security, X-Content-Type-Options, Link and Vary. Each gets a pass, a warning or a blocking flag with a one-line reason, and any other headers are listed underneath. Pasted headers are graded on your own machine; nothing is uploaded.

How to use it

1. In a terminal, run curl -I followed by your URL and copy everything it prints.
2. Paste it into "Or paste headers" and click "Analyze Headers".
3. Read the status line, the table and the result line, which counts blocking issues and warnings.
4. The "Quick Live Check" button, next to the "URL" field, only confirms that a page loads through a public CORS proxy. A browser cannot read another site's response headers, so that check shows the proxy's status code, not your server's, and it sends the URL you type to the proxy.

What the grades mean

The only blocking flag is an X-Robots-Tag containing noindex or none, because that keeps the URL out of search indexes whatever the HTML says. The status line gets a check mark for 2xx, a warning for 3xx and a cross for 4xx or 5xx; the totals count header issues only. Warnings cover a missing Content-Type or one without a charset, a missing or no-store/no-cache Cache-Control, no Content-Encoding (curl -I may hide compression; add --compressed), no HSTS header, no X-Content-Type-Options, and a Vary header that includes User-Agent. A canonical sent in a Link header is shown so you can confirm it.

Paste one response at a time. If you paste a redirect chain from curl -IL, the tool reads the last status line and, when a header repeats, keeps the last value, so earlier hops blur together. A warning is a prompt to confirm the setting was deliberate, not proof of a problem.

Related guide: HTTP Header Optimization for SEO