- Free, no sign-up
- Every header explained
- As Googlebot and a browser
Free HTTP Header Checker
Response headers can carry a noindex, a canonical or a hreflang set your HTML never shows, and they decide whether Google gets a 304, whether the page is compressed and how safe it is. Paste a URL (a page, a PDF or an image) and see every header explained in plain words, grouped into indexing, caching, compression and security, with the fix for each problem and what Googlebot gets compared with a browser. No sign-up.
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How to use it
Check, read, fix
Paste the URLs
Pages, PDFs or images, up to 10 at once. For each one we fetch the final response as a browser and as Googlebot smartphone, ask for Brotli, gzip and no compression in turn, and send the ETag back the way Google does to see whether the server answers 304.
Read what differs, then the groups
First what the server sends a browser next to what it sends Googlebot, with the differences marked; then the two tests; then every header explained in four groups: indexing, caching, compression and security.
Copy the fix for your server
Each problem comes with the reason and the line for Apache, Nginx, Cloudflare or WordPress. Fix, then check again.
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Quick answer
What does an HTTP header checker do?
An HTTP header checker requests a URL and shows the response headers the server sends before the page itself: the status, the content type, caching rules, compression and security settings, and any robots or canonical rules sent as headers. For SEO the headers that matter are X-Robots-Tag (a noindex there removes the page from Google even if the HTML is clean), Link rel=canonical and hreflang, and ETag or Last-Modified, which let Google recrawl with a 304 instead of a full download. This tool reads each header, explains it and flags the problems with the fix.
The headers that change indexing
Invisible in the browser, read by Google
| Header | What it does | Watch for |
|---|---|---|
| X-Robots-Tag | The robots meta rules as a header (noindex, nofollow, nosnippet, max-snippet and the rest); the only way to noindex a PDF or an image | A noindex left from staging; a rule for googlebot only |
| Link: rel="canonical" | A canonical as a header, for PDFs and other files | A value that disagrees with the HTML canonical |
| Link: rel="alternate"; hreflang | One of Google's three hreflang methods | Mixing it with HTML tags that say something else |
| Status | 200, a redirect or an error | An error page that answers 200, or a 404 for a real page |
An X-Robots-Tag can name a crawler: googlebot: noindex applies to Google only. Rules from the header and the meta tag add up, and the strictest wins.
Caching and 304s
Let Google skip what has not changed
Google's crawlers support ETag with If-None-Match and Last-Modified with If-Modified-Since, as the HTTP standard defines them. When the version matches, the server should answer 304 Not Modified with no body, which saves your server the work and Google the download. Google prefers ETag, because Last-Modified dates are easy to format wrongly, and uses it when both are sent (Google Search Central, December 2024). Cache-Control matters for browsers and CDNs: no-store on a public page sends every visit to the server.
Compression
gzip and Brotli
Compression usually cuts HTML, CSS and JavaScript by 70 to 80% on the wire, and Google's crawlers accept gzip, deflate and Brotli. Brotli is usually 15 to 20% smaller than gzip for text. The test asks for each one separately, so you see what the server really offers, not only what your browser happened to get.
Security headers
Protection, not rankings
Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, X-Frame-Options or CSP frame-ancestors, Referrer-Policy and Permissions-Policy are not ranking signals. HTTPS is part of page experience; these headers protect visitors and the site. We list what is missing and why, without a letter grade, and point out headers that give away software versions.
FAQ
Questions people ask
How do I check the HTTP headers of a website?
Run curl -I with the URL, open the Network tab in Chrome DevTools and click the page, or paste the URL here to see every header explained, as a browser and as Googlebot.
What is X-Robots-Tag?
Robots rules sent as an HTTP header instead of a meta tag. It is the only way to noindex a PDF, an image or a video, and it can name one crawler.
How do I check if gzip or Brotli is enabled?
Ask the server for each encoding and read Content-Encoding in the answer. The compression test here does it for Brotli, gzip and none, with the size of each.
Do HTTP headers affect SEO?
X-Robots-Tag, Link canonical and hreflang, the status and caching do. Security headers do not rank; they protect.
What does Cache-Control: no-cache mean?
A copy may be kept but must be checked with the server before each use (cheap with a 304). no-store means no copy at all.
What is an ETag?
A version tag the server sends with a file. Google sends it back on the next crawl and wants a 304 with no body when nothing changed.
Why does my page show noindex only in the header?
A rule in the server config, the CDN or a security plugin, very often left from a staging site. The HTML looks clean, so nobody notices until pages drop out.
Which security headers should a site have?
Strict-Transport-Security once https works everywhere, X-Content-Type-Options: nosniff, X-Frame-Options or CSP frame-ancestors, a Referrer-Policy, and a Content-Security-Policy when you are ready to test one.
What is the Vary header?
It tells caches which request headers change the answer: Accept-Encoding when the server compresses, User-Agent only when phones get different HTML.
Why are my headers different for Googlebot?
A CDN rule, bot protection or a caching plugin that answers bots differently. The side-by-side view shows exactly which headers change.
Keep going
More free tools and guides
- HTTP Status Checker: status codes, every redirect hop and the raw headers for 10 URLs.
- Noindex Tag Checker and Canonical Tag Checker: the HTML side of the same signals.
- Redirect Checker: chains, loops and 301 vs 302.
- Website Speed Test and SSL Checker.
- Indexing controls and HTTP headers (Advanced, chapter 4) and site migrations (chapter 6).
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Read what your server really sends
Every header explained, as a browser and as Googlebot. Free, no sign-up.