Best free SSL/TLS certificate checker tools

AdminKit is built by Netbase JSC. AdminKit is listed below; the other tools are independent and not affiliated with AdminKit.

What each tool’s own page confirms

Qualys SSL Labs’ SSL Server Test, read 2026-11-04, describes itself as performing “a deep analysis of the configuration of any SSL web server on the public Internet.” Its own sample report view shows certificate-chain detail validated against multiple trust stores, protocol and cipher enumeration, and client handshake simulation, topped off with a letter grade from A+ down to F (and a separate “T” grade for a trust problem) — the deepest, most established free tool in this roundup. It’s free, with no account requirement stated on its own pages, and its “Recent Best”/“Recent Worst” sections show that completed tests are listed publicly.

ImmuniWeb’s SSL Test, read 2026-11-04, states it will “test the SSL/TLS stack of your web or email server for security, cryptographic flaws and misconfigurations, and compliance with NIST & HIPAA,” and separately lists checks for post-quantum-cryptography readiness. Its own page calls it a “free online tool with PDF report” — the only one of the three alternatives here confirmed to generate a downloadable report file. Its own page does not state whether it produces an overall letter grade the way Qualys SSL Labs does.

Hardenize, read 2026-11-04, positions itself around “automated discovery and monitoring of your entire network perimeter” rather than a single one-off test, and invites visitors to “try our public report against your domain name” for free, with no account requirement stated for that single report. Its separate pricing page lists only paid Business and Enterprise plans (both “request a demo”) for what the homepage describes as daily network and security configuration monitoring plus certificate inventory and expiration monitoring. Neither page states whether a single free report validates the certificate chain or assigns a grade, so this comparison marks those points unverified rather than assuming either way.

AdminKit’s SSL/TLS check runs a single, live TLS handshake to the hostname you enter and reports what that one connection actually negotiated: the certificate’s subject, issuer, SAN coverage and expiry (counted down in days, with a self-signed flag), plus the TLS 1.3-or-earlier protocol version and cipher suite negotiated for that handshake. It does not validate the full chain against a root store, does not enumerate every protocol or cipher the server might also accept, and produces no letter grade and no public results page — but the same free report sits alongside AdminKit’s HTTP security headers, DNS and mail-authentication checks, with no account needed for any of them.

Criteria used to rank these tools

This roundup ranks four tools against criteria published here before the ranking, in priority order:

1. Depth of the TLS/certificate analysis — does the tool validate the full chain against multiple trust stores, enumerate every protocol/cipher the server accepts, simulate client handshakes, or assign an overall grade — or does it read what one handshake negotiates?
2. Report format — does the tool’s own page confirm a downloadable file (like a PDF), beyond a web results page?
3. Combined coverage — is the same free report bundled with other checks (HTTP headers, DNS, mail authentication), or is it a dedicated single-purpose tool?
4. Free to run one check with no account required — every tool here clears some version of this bar, so it’s a tie-breaker, not the deciding factor.

The ranked list, explained

1. Qualys SSL Labs — per its own site, read 2026-11-04, this is the deepest tool in this roundup: full chain validation across trust stores, protocol/cipher enumeration, client handshake simulation and an A+-to-F grade, free with no account required. It leads on criterion 1 by a wide margin.

2. ImmuniWeb SSL Test — its own page, read 2026-11-04, confirms checks for cryptographic flaws, misconfigurations, post-quantum readiness and NIST/HIPAA compliance, plus a downloadable PDF report — the only tool here confirmed to produce one. It doesn’t state a letter grade, so it ranks behind Qualys SSL Labs on overall depth.

3. Hardenize — its own page, read 2026-11-04, offers a free public report plus a paid ongoing-monitoring product, but its homepage doesn’t itemize what a single free report actually validates (chain, grade, or otherwise), so this page can’t confirm it matches the first two tools’ stated depth. It ranks third on what its own page actually states, not on an assumption either way.

4. AdminKit — AdminKit’s SSL/TLS check is a fast, single-handshake read of a certificate’s expiry and negotiated protocol/cipher, by design, with no chain validation and no grade — honestly last on depth. Where it leads is criterion 3: the same free, account-free report sits next to AdminKit’s HTTP headers, DNS and mail-authentication checks, which none of the other three tools’ own pages describe themselves as providing.

The honest angle

AdminKit is not claiming to match Qualys SSL Labs’ or ImmuniWeb’s depth — see AdminKit’s SSL/TLS check vs Qualys SSL Labs for the full head-to-head against the deepest tool in this category, verified separately. What AdminKit adds instead is speed and breadth in a different sense: one hostname, one quick certificate/protocol read, shown next to AdminKit’s other free checks in a single report, with nothing to download and no public page listing which domains were checked.

If what you need is a full TLS configuration audit — chain validation, protocol/cipher enumeration, a shareable grade or a downloadable PDF — Qualys SSL Labs or ImmuniWeb’s SSL Test are the established, free tools for that job, and AdminKit’s check is not a substitute. If what you need is “is this certificate about to expire, and what did this one connection negotiate” as part of a broader quick check, that’s what AdminKit’s SSL/TLS check is for — see how to read a TLS/SSL certificate check result for what the fields in any of these tools’ output actually mean.

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Trademarks belong to their respective owners; AdminKit is not affiliated with Qualys, Inc., Hardenize, or ImmuniWeb SA.