Get an A+ to F security grade for any website. Audits 8 critical security headers against OWASP best practices — CSP, HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy, and more. Includes the exact header value to add for every missing header.
Audits 8 critical security headers against OWASP recommendations. Enter any page on your site.
Enter any live webpage URL — the tool fetches the actual HTTP response headers exactly as your server sends them, just like a browser would see.
Your site receives a letter grade from A+ to F based on how many security headers are present and correctly configured. Each header shows its current value, what attack it prevents, and a pass/warn/fail status.
Every missing or misconfigured header shows the exact recommended value to add — click Copy to grab it. Pass this to your server admin or add it to your nginx/Apache config, CDN settings, or application middleware. Then re-check to confirm your grade has improved.
The invisible layer of protection that separates secure websites from vulnerable ones
HTTP security headers are response headers that your server sends to browsers alongside every page. They are invisible to regular visitors but act as a set of strict instructions that tell browsers exactly what they are and are not allowed to do on your website. Without them, browsers operate in a permissive default mode that leaves your site open to a range of well-documented attacks.
Security headers cost nothing to implement. They require no third-party service. They take minutes to add to a server configuration file. Yet most websites are missing most or all of them. A missing Content Security Policy leaves your site open to cross-site scripting attacks. A missing Strict-Transport-Security header leaves users vulnerable to protocol downgrade attacks even on HTTPS sites. A missing X-Frame-Options header lets attackers embed your pages in invisible iframes to hijack user clicks.
Security headers are also a trust signal. Browsers, security scanners, enterprise procurement tools, and even some search engine crawlers check for their presence. A website missing critical security headers can be flagged as insecure by browser security extensions, corporate network filters, and vulnerability scanners used by potential clients or partners. For any site handling user data, running e-commerce, or operating in a regulated industry, missing security headers is a compliance risk as well as a security risk.
The first step is knowing where you stand. The Visiblytics Website Header Security Checker audits your site against the eight most critical security headers defined by OWASP, gives you a letter grade from A+ to F, and shows you the exact header value to copy and add for every missing header. You can go from an F grade to an A grade in the same afternoon.
Every header explained in plain English with the attack it prevents and why it matters
The Visiblytics Website Header Security Checker audits eight headers defined by OWASP as the most critical for web application security. For each one the tool shows whether it is present, what its current value is, what attack it prevents, and the exact recommended value to add if it is missing.
Step-by-step instructions to fix every missing header the checker finds
The Visiblytics checker shows the exact recommended header value for every missing header with a one-click copy button. Once you have copied the value, the method of adding it depends on how your site is hosted and configured. Here are the steps for the four most common setups.
Every website type that handles users, data, or transactions has something to lose from missing headers
Security headers are not just a concern for large enterprises or technical developers. Every website that has users interacting with it has something to protect. Here is how different types of website owners benefit from checking and fixing their security headers.
WordPress powers over 40 percent of all websites on the internet and is the most targeted CMS by attackers. Most WordPress installations ship with no security headers configured by default. The server, X-Powered-By, and sometimes the WordPress version itself are all exposed in HTTP headers out of the box. Running the checker on a fresh WordPress installation almost always returns an F grade. Fixing this takes under 30 minutes with a plugin or a few lines in .htaccess.
Online stores processing payments are high-value targets for Magecart and similar card-skimming attacks, which typically work by injecting malicious JavaScript into checkout pages. A properly configured Content-Security-Policy that restricts which scripts are allowed to execute is one of the most effective defences against this type of attack. PCI DSS compliance guidance also references security headers as part of a secure web application configuration.
Applications with user login, sessions, and sensitive data have the most to lose from XSS and clickjacking attacks. A missing CSP on a SaaS application means that if an attacker finds any XSS vector, they can execute arbitrary JavaScript in the context of an authenticated user session. For any application handling personal data, missing security headers may also constitute a failure to implement reasonable technical security measures under GDPR.
Checking security headers on every site you build or manage is part of a responsible handover and ongoing maintenance process. Use the Visiblytics checker to run a quick audit before every site launch and after every major platform update. The copy-fix values feature means you can grab the exact recommended header string and drop it into the server configuration without needing to look anything up.
The honest feature-by-feature comparison of the three most used free security header checkers
There are three tools most commonly used to check website security headers. securityheaders.com is the most established, SerpWorx is widely linked to, and the Visiblytics checker is the newest but the most actionable of the three. Here is what each one actually does.
| Feature | Visiblytics | securityheaders.com | SerpWorx |
|---|---|---|---|
| Letter grade (A+ to F) | ✓ Yes | ✓ Yes | ✗ Numeric score only |
| Attack type explained per header | ✓ Every header | ✗ Not shown | ✓ Partial descriptions |
| Exact fix value with copy button | ✓ Every missing header | ✗ Not provided | ✓ Code snippets shown |
| Validates header values vs best practices | ✓ OWASP-aligned | ✓ Yes | ✗ Presence only, no validation |
| Server info leakage detection | ✓ Server and X-Powered-By flagged | ✓ Yes | ✗ Not checked |
| Results public by default | ✓ Private by default | ✗ Public unless hidden | ✓ Private |
| Part of a full SEO and web toolkit | ✓ 650+ free tools, no login | ✗ Security headers only | ✗ Limited free tools |
| Login required | ✓ Never | ✓ Not required | ✓ Not required |
The most important row in this table is header value validation. SerpWorx explicitly states on its own tool page that it only detects the presence of a header, not whether its value follows best practices. That means a Content-Security-Policy set to wildcard or an HSTS header with a max-age of zero will pass SerpWorx’s check even though both represent serious misconfigurations. The Visiblytics checker and securityheaders.com both validate header values against published best practices, giving you a result you can actually trust.
The other notable difference is that securityheaders.com makes your scan results public by default and shows them in a global recent scans feed. If you are auditing a site with a poor security posture and prefer not to advertise that publicly, the Visiblytics checker keeps your results private by default.
Check your security grade now. Enter your URL above, get your A+ to F grade in seconds, and copy the exact fix values for every missing header — completely free, no account needed, results stay private.
The grade starts at 100 points. Missing critical headers (CSP, HSTS, X-Content-Type-Options, X-Frame-Options) each deduct 20 points. Missing medium-priority headers (Referrer-Policy, Permissions-Policy) deduct 10 points. Server information leakage (X-Powered-By, detailed Server header) deducts 5 points each. The final score maps to A+ (95+), A (85+), B (70+), C (55+), D (40+), F (below 40).
CSP is the single most powerful security header. It tells the browser exactly which sources are allowed to load scripts, styles, images and other resources. A well-configured CSP prevents Cross-Site Scripting (XSS) attacks — one of the most common web vulnerabilities — by blocking execution of injected malicious scripts.
HSTS tells browsers to always connect to your site over HTTPS — even if the user types http://. Once a browser has seen your HSTS header, it refuses to connect over HTTP at all, preventing protocol downgrade attacks and cookie hijacking. The recommended min-age is 31536000 (1 year) with includeSubDomains.
X-Frame-Options prevents your page from being embedded in an iframe on another website. Without it, attackers can overlay an invisible iframe on a malicious page that tricks users into clicking your buttons — a technique called clickjacking. The Content-Security-Policy frame-ancestors directive offers more granular control and is the modern replacement.
Setting this header to nosniff prevents browsers from MIME-type sniffing — guessing what type of content a response contains. Without it, a browser might interpret an uploaded text file as executable JavaScript. This header is one of the simplest to add and should be on every production website.
The method depends on your server: For nginx, add header directives to your server block. For Apache, use Header set directives in .htaccess or httpd.conf. For Cloudflare, use Transform Rules. For WordPress, many security plugins add headers automatically. For Node.js, use the Helmet middleware. This checker shows the exact header name and recommended value to configure.
