Security Header Checker: A Simple Guide for Website Owners

Security headers are HTTP response headers sent from a web server to a browser alongside page content. They instruct the browser how to handle the page securely: whether the page can be embedded in an iframe on another domain, whether resources can be loaded from third-party origins, whether the browser should always use HTTPS, and how much referral information is shared when visitors click external links.

These instructions add a layer of browser-level protection that complements other security practices. They do not fix application code vulnerabilities or replace authentication security — but they reduce the attack surface available through browser behavior. For most business websites, having the right headers in place is a meaningful baseline of security hygiene.

MonitorMojo helps monitor uptime, SSL, response time, and basic website risk signals including security headers, but it does not replace a professional security audit or penetration test. The headers most relevant to business websites are HSTS, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, and Content-Security-Policy.

Strict-Transport-Security (HSTS) tells browsers to always connect to the site over HTTPS, even if the visitor types an HTTP URL or follows an old HTTP link. Without HSTS, a browser might follow an HTTP bookmark to the unencrypted version of the site. HSTS prevents this downgrade and is considered one of the highest-priority security headers to configure.

X-Frame-Options prevents the page from being loaded inside an iframe on another domain. This stops clickjacking attacks, where a malicious page overlays your content with invisible elements that capture clicks intended for your buttons or forms. X-Content-Type-Options: nosniff tells browsers not to guess content types — protection against injection attacks that exploit browser content sniffing behavior.

Referrer-Policy controls how much URL information is shared with external sites when visitors click away from your page. Without a policy, browsers may send the full URL including sensitive query parameters to the destination. Content-Security-Policy is the most powerful header — it specifies which domains can load scripts, images, and other resources — but also the most complex to implement correctly.

Security headers are configured at the server or CDN level — in nginx configuration, Apache .htaccess rules, Cloudflare page rules, or load balancer settings. When a website migrates to a new server, the page content usually transfers correctly while the server-level configuration does not. The site looks identical to visitors, but the headers are gone.

For WordPress sites, security headers are often configured through security plugins. When a plugin is deactivated, removed, or conflicts with another plugin, its header configuration disappears too. Without a specific check, this loss is completely invisible — the site looks the same and works the same, but the browser-level protections are no longer present.

Running a security header check immediately after any hosting migration, CDN change, or major plugin update catches this regression before it creates an extended gap. The check takes seconds and catches a category of problem that would otherwise go unnoticed for months.

Security headers are visible in the HTTP response from the server. Any tool that makes a real HTTP request and reads the response headers can surface them. In a browser's developer tools, the Network tab shows all response headers for any page load — you can look there manually for the specific header names.

For a more structured check, an external website health check tool that specifically reviews security headers gives you a clear pass or missing status for each header type without requiring you to parse raw responses. MonitorMojo includes security header status as part of its standard health check alongside reachability, SSL, and response time.

If headers are missing, how you add them depends on your hosting environment. For WordPress: add through a security plugin or .htaccess file. For nginx or Apache: add in the server configuration file. For Cloudflare: configure through the Transform Rules or Security Headers feature. After adding headers, run an external check to confirm they appear in the live server response.

• Check security headers as part of every monthly health review
• Always run a header check immediately after any hosting migration or CDN change
• Check after major WordPress plugin updates that touch security configuration
• Verify headers are present on subdomains separately — headers on root domain do not auto-apply
• After adding headers, run an external check to confirm visibility from outside the server

For agencies delivering website care plans, security header status is a concrete deliverable clients can understand without a technical background. The message to clients is simple: 'Your website has the key browser security protections in place. We check these monthly as part of your care plan and address any changes immediately.'

Including security header status in monthly reports makes the care plan's security layer visible. Clients in regulated industries — healthcare, finance, legal services — particularly value this kind of documented security hygiene evidence, even at the basic configuration header level.

Security header monitoring is also useful as a change detection signal. If a header disappears between one monthly check and the next, you know something changed in the server configuration during that period. That narrows the investigation considerably compared to discovering headers are missing without any sense of when they were last present.