HTTP Header Viewer
How to use HTTP Header Viewer
- 1
Enter the website URL
Type the full URL, including https://, of the site whose headers you want to inspect.
- 2
Fetch the headers
Click "Fetch Headers" to retrieve the HTTP response headers returned by that URL.
- 3
Review the response
Read the overview showing status code, response time, and total header count, then scan the full list of header names and values.
- 4
Copy all headers
Use "Copy All Headers" to send the complete header list to your clipboard for debugging or documentation.
Reading HTTP Response Headers Like a Pro
What HTTP headers are
Every time a browser requests a web page, two sets of metadata travel alongside the actual content: request headers, sent by the browser, and response headers, sent back by the server. Headers are simple name-and-value pairs, such as Content-Type: text/html, that describe the message rather than being part of the visible page. They control caching, security, content negotiation, cookies, redirects, and much more. The page body is what you see; the headers are the instructions that tell the browser how to handle it.
This tool shows the response headers a server returns for a URL, along with the status code and how long the response took. Reading them is one of the fastest ways to understand how a site is configured, because so much behavior that is invisible on the page is spelled out explicitly in the headers.
Status codes: the first thing to read
Before any header, the status code tells you what happened. The 200 range means success, with 200 OK being the normal case. The 300 range means redirection: 301 is a permanent move and 302 or 307 are temporary, each accompanied by a Location header pointing to the new URL. The 400 range means a client-side problem, such as 404 Not Found or 403 Forbidden, while the 500 range means the server itself failed, as with 500 Internal Server Error or 503 Service Unavailable.
The status code frames everything else. A page that looks fine in a browser but returns a 404 or a soft error to crawlers will not get indexed, and a resource returning 500 intermittently signals a server problem worth investigating. Checking the raw status, rather than trusting the rendered page, catches issues that the browser quietly papers over.
Content and caching headers
Content-Type declares the media type and character set of the response, for example text/html; charset=utf-8 or application/json. A wrong Content-Type causes browsers to mishandle a response, such as offering an HTML page for download instead of displaying it. Content-Encoding reveals compression like gzip or br (Brotli), confirming that text assets are being sent efficiently. Content-Length gives the size in bytes.
Caching is governed mainly by Cache-Control, which spells out how long and where a response may be cached, with directives like max-age, public, private, and no-store. ETag and Last-Modified support conditional requests, letting a browser ask whether its cached copy is still fresh and receive a lightweight 304 Not Modified when nothing has changed. Misconfigured caching headers are a leading cause of both stale content and unnecessarily slow repeat visits, so they are worth inspecting closely.
Security headers worth checking
A cluster of response headers harden a site against common attacks, and their presence is a quick health check. Strict-Transport-Security (HSTS) forces browsers to use HTTPS for future visits, closing a downgrade-attack window. Content-Security-Policy (CSP) restricts which scripts, styles, and other resources may load, which is the strongest defense against cross-site scripting. X-Frame-Options (or the frame-ancestors directive in CSP) prevents your pages from being embedded in malicious iframes, defeating clickjacking. X-Content-Type-Options: nosniff stops browsers from guessing content types.
When auditing a site, the absence of these headers is itself informative. A site serving sensitive content with no HSTS, no CSP, and no X-Frame-Options has obvious hardening gaps. Viewing the headers makes the security posture visible at a glance, which is useful both for your own sites and for evaluating third parties.
Cookies, CORS, and the server fingerprint
Set-Cookie headers show what cookies a server is planting and with what flags. The Secure, HttpOnly, and SameSite attributes on a cookie determine whether it is sent only over HTTPS, hidden from JavaScript, and protected against cross-site requests, so reading them reveals whether session cookies are configured safely. The Access-Control-Allow-Origin header, part of CORS, tells you whether and from where a resource may be requested by scripts on other domains, which is essential when debugging why a front-end fetch is being blocked.
Other headers fingerprint the stack. Server names the web server software, X-Powered-By may reveal the application framework, and Via or CF-Cache-Status can expose a CDN like Cloudflare sitting in front of the origin. Many operators strip these to reduce information leakage, so what is present, and what is conspicuously absent, both tell a story.
Why inspecting headers matters for SEO and debugging
Several headers directly affect search. The X-Robots-Tag header carries the same directives as the robots meta tag, such as noindex and nofollow, but applies at the HTTP level, which makes it the only way to control indexing of non-HTML files like PDFs. A misplaced X-Robots-Tag: noindex left in production can silently deindex pages, and because it is invisible on the page itself, viewing the raw headers is often the only way to find it. The Link header can also declare a canonical relationship server-side.
For day-to-day debugging, headers are the ground truth. They confirm whether HTTPS is enforced, whether compression and caching are actually on, whether a redirect is the 301 you intended rather than a 302, and whether the server is returning the status code you expect. Because browsers block scripts from reading cross-origin headers, this tool fetches the URL through a server proxy so you can inspect any public page's response headers without those restrictions.
Frequently asked questions
What HTTP headers will this tool show me?
Why are HTTP headers useful for SEO and debugging?
Why does the URL need to include https://?
Why might a fetch return an error?
Is the tool free, and is the URL processed privately?
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