Every time a browser loads a page, the server responds with more information than what's visible: the HTTP headers. Among other things, this is where you find whether the site forces HTTPS, whether it allows itself to be loaded inside someone else's iframe, or what external resources it's allowed to execute. Reviewing those headers is one of the fastest ways to gauge how much care has gone into a site's security, whether it's yours or someone else's.
What security HTTP headers are
Beyond the usual headers (content type, encoding, caching), there's a group specifically designed to strengthen the browser's defenses against common attacks. The most relevant ones:
- HSTS (
Strict-Transport-Security): forces the browser to always use HTTPS with that domain, even if someone tries to force an insecure HTTP connection. - CSP (
Content-Security-Policy): defines which origins are allowed to load scripts, styles or images on the page, reducing the impact of an XSS attack even if a vulnerability exists. - X-Frame-Options: controls whether the page can be displayed inside an
<iframe>on another site, preventing clickjacking attacks. - X-Content-Type-Options: stops the browser from trying to "guess" a file's type, which can prevent certain attack vectors.
How to analyze a website's headers
- Enter the URL you want to analyze.
- The tool makes the request and shows the status code, response time and all headers received.
- Review the security analysis, which flags which headers are present and which are missing.
You can do it free with the HTTP headers checker on this site.
Why a missing header is a signal, not just a detail
A missing Strict-Transport-Security doesn't automatically mean the site is insecure, but it does mean it's not taking advantage of a free, available protection: any server can add this header at no cost and with no real technical complexity. The same goes for X-Frame-Options: without it, the site is potentially embeddable in a malicious iframe designed to trick the user (clickjacking). Checking what's missing is, in practice, a quick, low-effort improvement checklist.
The difference between analyzing your own site and someone else's
If it's your own project, this tool works as a pre-launch checklist: it confirms the server configuration includes the headers you believe you've added. If you're analyzing someone else's site, it's public information (any browser receives it when loading the page), useful for gauging a provider's technical seriousness or understanding why a site behaves a certain way (for example, why it can't be embedded in an iframe).
Frequently asked questions
Is analyzing another site's headers "hacking"? No, it's data the server itself publicly sends to any browser that connects; nothing private is being accessed.
Which header matters most? It depends on context, but HSTS and CSP tend to have the biggest impact on real security against common attacks.
Why shouldn't my site appear in someone else's iframe? Without X-Frame-Options or its CSP equivalent, an attacker can display your site inside an invisible iframe overlaid on other content, tricking the user into clicking without knowing what site they're really interacting with.
Is anything from my query saved? No, the request is made from your browser and only you see the result.
Analyze any website's security headers for free with the HTTP headers checker, with HSTS, CSP and X-Frame-Options evaluation.