Best free HTTP security header analyzers
AdminKit's free HTTP security-headers check reports each recommended response header present or missing, with its actual value and a plain-language fix hint; SecurityHeaders.com and Mozilla's HTTP Observatory instead compute a single letter grade, and Hardenize folds headers into a much broader free TLS, DNS and mail-security report.
AdminKit is built by Netbase JSC. AdminKit is listed below; SecurityHeaders.com, Mozilla’s HTTP Observatory and Hardenize are independent and not affiliated with AdminKit.
What each tool’s own page confirms
SecurityHeaders.com, a Snyk project per its own footer, grades a URL’s response headers A+ down to F (with an “R” grade for a redirect result) and has logged more than 405 million scans. A sample report for scotthelme.co.uk shows the specific headers it evaluates: Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, X-XSS-Protection, Referrer-Policy, Permissions-Policy, Cross-Origin-Resource-Policy and X-Frame-Options, among others. Its own homepage offers a free scan with no account requirement stated. SecurityHeaders.com’s Cloudflare bot-check blocked a fresh automated read on 2026-11-04; the facts above were confirmed 2026-10-29 for AdminKit vs SecurityHeaders.com, which carries the full head-to-head breakdown.
Mozilla’s HTTP Observatory, read 2026-11-04, launched in 2016 and is operated by Mozilla itself. Per its own FAQ, it scores a site’s HTTP headers with both a numeric score and a letter grade (its worked example shows 105 and A+), testing Content-Security-Policy, Strict-Transport-Security, X-Frame-Options, X-Content-Type-Options, Referrer-Policy and Cross-Origin-Resource-Policy. The same FAQ states plainly that the current version does not check TLS or certificate data — those checks were removed from an earlier version — and that scanning is free, needs no account, and only works against a publicly reachable site, since every result is public. Mozilla’s own homepage cites 6.9 million sites analyzed and 47 million scans since launch.
Hardenize, read 2026-11-04, is operated by Red Sift and offers a free public report for any domain with no login shown on the report page itself — its pricing page lists only paid Business and Enterprise tiers, which add continuous monitoring on top of the one-off report. A sample public report shows HTTP response headers (Strict-Transport-Security, Content-Security-Policy, X-Content-Type-Options, X-XSS-Protection and more) with their exact sent values, each rated good/error/neutral individually rather than combined into one grade — alongside a much wider set of checks: full DNS records (including DNSSEC and DANE), TLS/SSL protocol and cipher-suite configuration, and mail-security records (SPF, DMARC, MTA-STS, TLS-RPT) for any mail servers found.
The honest angle
These three tools and AdminKit’s check don’t all do the same job. If what you want is a single, widely recognized letter grade, SecurityHeaders.com and Mozilla’s HTTP Observatory both provide one, with scan volume neither AdminKit nor Hardenize states matching. If what you want is one free report that also covers TLS, DNS and mail authentication alongside headers, Hardenize’s public report goes furthest of the four. AdminKit’s HTTP security headers check doesn’t compute a grade and doesn’t fold in TLS/DNS/mail checks on the same page — what it does is show each recommended header’s exact value and a plain-language fix hint, next to AdminKit’s own SSL/TLS and DNS checks as separate free tools rather than one combined report.
None of this makes a “Present” result or a good grade a guarantee a site has no other vulnerabilities — see evaluating HTTP security header policy strength and HSTS and HSTS preload explained for what a present-but-weak header value actually looks like, something a letter grade or a good/error status alone doesn’t always make obvious.
Trademarks belong to their respective owners; AdminKit is not affiliated with SecurityHeaders.com, Snyk Ltd, Mozilla, Hardenize, or Red Sift.
| Feature | AdminKit | SecurityHeaders.com | Mozilla HTTP Observatory | Hardenize |
|---|---|---|---|---|
| Free, no account required to run a basic check | ✓ | ✓ | ✓ | ✓ |
| Gives a single overall letter grade (A+ to F) for the URL | — | ✓ | ✓ | ✗ |
| Shows the exact value of each header sent, not just present/missing | ✓ | — | — | ✓ |
| Checks TLS/SSL certificate configuration in the same report | — | — | ✗ | ✓ |
| Also checks DNS records and/or email authentication (SPF/DMARC) in the same report | — | — | — | ✓ |
| Publishes a usage/scan-volume statistic on its own page | — | ✓ | ✓ | — |
| Plain-language fix hint shown per missing or weak header | ✓ | — | — | — |
AdminKit vs SecurityHeaders.com
Free, no account required to run a basic check
Gives a single overall letter grade (A+ to F) for the URL
Shows the exact value of each header sent, not just present/missing
Publishes a usage/scan-volume statistic on its own page
Plain-language fix hint shown per missing or weak header
AdminKit vs Mozilla HTTP Observatory
Free, no account required to run a basic check
Gives a single overall letter grade (A+ to F) for the URL
Shows the exact value of each header sent, not just present/missing
Checks TLS/SSL certificate configuration in the same report
Publishes a usage/scan-volume statistic on its own page
Plain-language fix hint shown per missing or weak header
AdminKit vs Hardenize
Free, no account required to run a basic check
Gives a single overall letter grade (A+ to F) for the URL
Shows the exact value of each header sent, not just present/missing
Checks TLS/SSL certificate configuration in the same report
Also checks DNS records and/or email authentication (SPF/DMARC) in the same report
Plain-language fix hint shown per missing or weak header
Frequently asked questions
Does AdminKit give a single grade like SecurityHeaders.com or Mozilla's HTTP Observatory?
No. SecurityHeaders.com's own example report grades a URL A+ down to F, and Mozilla's HTTP Observatory FAQ describes a numeric score (e.g. 105) paired with a letter grade (e.g. A+). AdminKit's HTTP security headers check instead lists each recommended header (CSP, HSTS, X-Content-Type-Options, X-Frame-Options, Referrer-Policy, Permissions-Policy) as present or missing, shows the exact value sent for each one present, and adds a plain-language fix hint — a checklist rather than a single score.
Why doesn't AdminKit's headers check also cover TLS, DNS or email authentication the way Hardenize's report does?
Hardenize's own public report (read 2026-11-04) combines HTTP response headers with full TLS/cipher-suite configuration, DNS records including DNSSEC and DANE, and mail-security records (SPF, DMARC, MTA-STS, TLS-RPT) on one page — a much wider scope than a headers-only check. AdminKit covers that same ground today, just as separate free tools: [SSL/TLS check](/tools/ssl-check/), [DNS lookup](/tools/dns-lookup/) and [SPF check](/tools/spf-check/) rather than one combined report. That's a deliberate split, not a missing feature AdminKit is pretending not to have.
AdminKit already has a page comparing it to SecurityHeaders.com directly — why a second comparison?
The two pages answer different questions. [AdminKit vs SecurityHeaders.com](/compare/vs-securityheaders-com/) is a one-on-one deep dive into that single competitor's grading system and scan volume. This page is the wider category roundup: how AdminKit's check stacks up against three of the most-used free header/security analyzers (SecurityHeaders.com, Mozilla's HTTP Observatory, Hardenize) side by side. Nothing here is claimed again in more detail than the head-to-head page already covers — see that page for SecurityHeaders.com's full breakdown.
Do SecurityHeaders.com and Mozilla's HTTP Observatory show the exact header value sent, not just present/missing, the way AdminKit and Hardenize do?
Unverified, honestly. SecurityHeaders.com's Cloudflare bot-check blocked a fresh automated read on 2026-11-04 (the facts cited here come from the same public pages, confirmed 2026-10-29 for AdminKit's dedicated SecurityHeaders.com comparison), and Mozilla's HTTP Observatory FAQ, read 2026-11-04, doesn't state either way whether a scan result displays each header's literal sent value. This page marks that point unverified for both rather than assuming.
Is this page ranking these three tools from best to worst?
No. SecurityHeaders.com, Mozilla's HTTP Observatory and Hardenize solve overlapping but different jobs — a shareable letter grade, a Mozilla-maintained scoring standard, and a much broader free TLS/DNS/mail-security report that happens to include headers — so a single best-to-worst order would misrepresent what each is for. The table below states what each tool's own page confirms, so you can match the tool to your actual need.
Does this page use SecurityHeaders.com's, Mozilla's or Hardenize's/Red Sift's logo or brand assets?
No. All three names are used only to identify and compare publicly available services (nominative use). AdminKit is not affiliated with or endorsed by SecurityHeaders.com, Snyk Ltd (which operates it), Mozilla, Hardenize, or Red Sift (which operates Hardenize).
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