Best Free Security Headers Checkers Compared (2026)
Five popular tools, one comparison. See which security headers checker gives you the deepest analysis, the most actionable results, and the best value for your workflow.
Security headers are HTTP response headers that instruct browsers how to handle your website's content. They control which scripts can run, whether your pages can be embedded in frames, and how cookies travel across the network. Checking them regularly is one of the simplest ways to strengthen your site's defenses.
Several free tools exist for this job, each with different strengths. Some focus purely on header presence. Others evaluate configuration quality, check TLS certificates, or audit cookies. This guide compares the five most widely used options so you can pick the right tool for your needs.
What to look for in a security headers checker#
Not all header checkers do the same thing. Before comparing specific tools, it helps to know which criteria actually matter. Here is what separates a basic presence check from a genuinely useful analysis.
- Number of headers checked. Some tools look at six to eight common headers. Others evaluate 15 or more, including newer standards like Cross-Origin-Opener-Policy and Permissions-Policy.
- Analysis depth. A header can be present and still misconfigured. The best tools evaluate the actual values, not just whether the header exists. A Content-Security-Policy that includes unsafe-inline, for example, offers very little protection.
- Additional checks. TLS certificate configuration, DNS security records (SPF, DKIM, DMARC), and cookie attributes (HttpOnly, Secure, SameSite) all affect your security posture. Tools that check these alongside headers save you from juggling multiple scanners.
- Actionable recommendations. Knowing a header is missing is useful. Knowing exactly what value to set, with copy-paste examples for your web server, is far more useful.
- Reporting and export. If you need to share results with a team or include them in a compliance workflow, PDF export and structured data formats matter.
- API availability. Teams that want to integrate header checks into CI/CD pipelines or scheduled monitoring need a programmatic interface, not just a web form.
- Free tier limits. Most tools offer free scans, but the scope varies. Some cap the number of scans per day. Others restrict features like PDF reports or API access to paid plans.
With these criteria in mind, let's look at how each tool measures up.
Comparison overview#
The table below compares all five tools across the criteria described above. Green checks indicate full support. Red marks indicate the feature is not available.
| Feature | SiteSecurityScore | SecurityHeaders.com | Mozilla Observatory | HeaderScan | Qualys SSL Labs |
|---|---|---|---|---|---|
| Headers checked | 15+ | ~8 | ~10 | ~8 | None |
| TLS/SSL analysis | |||||
| DNS security checks | |||||
| Cookie audit | |||||
| CSP deep analysis | |||||
| Fix recommendations | |||||
| PDF export | |||||
| API access | Ending 2026 | ||||
| Browser extension | |||||
| Free tier | Unlimited scans | Unlimited scans | Unlimited scans | Unlimited scans | Unlimited scans |
Tool by tool breakdown#
SiteSecurityScore
sitesecurityscore.comSiteSecurityScore takes a full stack approach. A single scan checks over 15 HTTP security headers, evaluates your TLS/SSL configuration, audits DNS security records (SPF, DKIM, DMARC), reviews cookie security attributes, and performs a deep Content Security Policy analysis that flags overly permissive directives, missing fallbacks, and unsafe sources.
Results include actionable fix recommendations with server specific configuration examples. You can export a PDF report for compliance or team review. A REST API is available for CI/CD integration and scheduled monitoring. The Chrome extension lets you scan pages behind authentication walls, something no server-side scanner can reach.
Free unlimited scans on the web interface. API access and PDF reports are available through paid plans.
SecurityHeaders.com
securityheaders.comCreated by Scott Helme and now maintained by Snyk, SecurityHeaders.com pioneered the header checking space and remains one of the most recognized names in the category. It checks approximately eight core security headers and assigns a letter grade from A+ to F. The interface is clean and results appear almost instantly.
The tool focuses exclusively on HTTP response headers. It does not analyze TLS configuration, DNS records, or cookie attributes. Header values are reported but not deeply evaluated for configuration quality. There is no PDF export or fix recommendation engine.
Snyk announced that the SecurityHeaders.com API will be discontinued in April 2026. The free web scanner is expected to remain available, but teams relying on the API for automated workflows will need to migrate to another provider.
Mozilla HTTP Observatory
developer.mozilla.org/observatoryMozilla Observatory is an open source project that checks security headers alongside other web best practices. It evaluates Content Security Policy in depth, checks cookie flags, validates redirect behavior, and verifies that resources are loaded over secure connections. The scoring methodology is well documented and transparent.
The tool provides solid recommendations for each finding. It does not check TLS configuration or DNS security records. There is no PDF export, and the current version does not offer a public API. The interface is functional but less polished than some commercial alternatives.
Fully free with no usage limits. As an open source project backed by Mozilla, the methodology and source code are available for inspection.
HeaderScan
headerscan.comHeaderScan offers a clean, straightforward interface for checking common security headers. It checks approximately eight headers and provides basic recommendations for missing ones. The results are easy to read and well organized.
The feature set is lighter than some alternatives. There is no TLS analysis, DNS checking, cookie audit, or CSP deep dive. It does not offer PDF export, API access, or a browser extension. For teams that need a quick spot check of the most common headers, it gets the job done efficiently.
Free to use with no account required.
Qualys SSL Labs
ssllabs.comQualys SSL Labs is the industry standard for TLS/SSL analysis. It performs an exhaustive evaluation of your certificate chain, supported cipher suites, protocol versions, and known vulnerabilities like BEAST, POODLE, and Heartbleed. The depth of its TLS analysis is unmatched by any other free tool.
However, SSL Labs is focused specifically on TLS and does not analyze HTTP security headers. If your goal is to check whether your site has Content-Security-Policy, HSTS, or X-Frame-Options, you will need a separate tool. It also does not check DNS records or cookie attributes.
Free to use. Scans can take one to two minutes because the analysis is thorough. No API is available in the free tier.
Which tool should you use?#
The right choice depends on what you are trying to accomplish. Here is a quick guide based on common use cases.
- For comprehensive analysis. SiteSecurityScore covers headers, TLS, DNS, cookies, and CSP in one scan, so you get a complete picture without switching between tools.
- For a quick header spot check. SecurityHeaders.com is fast and gives you a letter grade in seconds. It is a good starting point when you just want to see which headers are present.
- For TLS deep dive. Qualys SSL Labs is the best choice when you need detailed certificate, cipher suite, and protocol analysis.
- For CI/CD automation. The SiteSecurityScore API returns structured JSON and integrates cleanly into deployment pipelines, letting you catch header regressions before they reach production.
- For open source transparency. Mozilla Observatory publishes its scoring methodology and source code, making it a strong option when you need to understand or audit the evaluation logic.
Worth knowing
You do not have to pick just one tool. Many security teams run SiteSecurityScore for their primary analysis and cross reference with Qualys SSL Labs for TLS specifics or Mozilla Observatory for a second opinion on CSP configuration. Different tools catch different things, and using more than one gives you better coverage.
FAQ#
Which security headers checker is the most accurate?
Accuracy depends on what you need to measure. For HTTP security header presence, most tools agree. Where they differ is analysis depth. Tools like SiteSecurityScore and Mozilla Observatory evaluate whether headers are configured correctly, not just whether they exist. A tool that only checks for presence will report a Content-Security-Policy with unsafe-inline as passing, while a deeper analysis tool will flag it as a weakness.
Are free security headers checkers safe to use?
Yes. Reputable security header checkers only send a standard HTTP request to your URL and read the response headers, the same information any browser receives when visiting your site. They do not probe for vulnerabilities, inject payloads, or access private data. The tools listed in this comparison are all well established and safe to use on production websites.
Can I automate security header checks?
Yes. SiteSecurityScore offers a REST API that returns structured JSON results, making it straightforward to integrate into CI/CD pipelines, scheduled monitoring, or compliance dashboards. SecurityHeaders.com had an API, but it is being discontinued in April 2026. Mozilla Observatory's current version does not offer a public API.
How often should I check my security headers?
At minimum, check after every deployment, infrastructure change, or CDN configuration update. Ideally, set up daily automated monitoring so you are alerted immediately if a header is removed or misconfigured. Deployments, CMS updates, and platform migrations can silently strip headers that were previously in place.
References
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