Zero Snippet

SSL certificate checker for TLS expiry, issuer & chain

Run a quick SSL/TLS certificate check on any public hostname: see certificate expiration, Subject Alternative Names (SANs), issuer and subject, SHA-256 fingerprint, negotiated TLS version, and whether our server considers the certificate chain trusted. Built for DevOps rotations, pre-launch QA, and HTTPS troubleshooting when SEO or analytics traffic depends on clean TLS.

How to use this SSL checker

Type a bare domain (for example api.example.com) or paste a full HTTPS URL. If you omit the scheme, we assume HTTPS. For plain http:// URLs without an explicit port, we still open port 443 so you inspect the certificate browsers use for TLS—matching how most production sites terminate SSL. After you submit, read the summary banner for days until expiry and trust status, then walk the numbered chain cards from leaf to root. Compare SANs with the hostnames you serve behind load balancers and CDNs, and keep fingerprints handy when validating a new issuance against your runbooks.

Why SSL certificate monitoring matters for sites and SEO

An expired or mismatched certificate breaks HTTPS, triggers browser interstitials, and can interrupt crawlers and analytics. Regular TLS certificate validation catches rotations that never deployed, partial chain uploads, or wrong wildcard coverage before customers notice. Pair hostname checks with our DNS lookup tool to confirm A/AAAA and CNAME targets, use the redirect chain checker when HTTPS hops through marketing domains, and follow HTTP behavior with the HTTP header checker and response code checker.

Reading certificate results: SANs, chain, and fingerprints

Modern clients validate hostnames against SAN entries, not only the legacy Common Name. When you migrate to a new CDN or add apex plus www, confirm every hostname your users type appears on the leaf or a matching wildcard. The intermediate certificates in the chain should link to a public root; missing intermediates cause intermittent “not secure” warnings. Fingerprints help you verify you are looking at the same cert your provider dashboard lists after reissuance. For page-level metadata and sharing previews after TLS is fixed, use our meta tags extractor and Open Graph preview.

Security notes and limitations

This tool connects from our infrastructure, not your laptop, so results reflect what our servers see—useful for public internet properties. We block private IP literals and hostnames that resolve to non-public addresses to reduce SSRF risk. Trust output follows our Node/OpenSSL trust store; enterprise roots or custom pinning may differ from end-user browsers. For link health after TLS is confirmed, run the broken link checker on key HTML pages.

Related free website tools

Browse the full website and URL tools section on the home page, or open a focused utility below.

  • Broken Link Checker — Scan outbound links from any URL for 404s and broken hrefs—paste a page and audit links in seconds.
  • HTTP Header Checker — Inspect HTTP response headers for any URL: cache control, content-type, CORS, and security-related values.
  • Redirect Chain Checker — Trace the full redirect path to the final URL and spot unnecessary hops hurting SEO and performance.
  • DNS Lookup Tool — Query A, AAAA, MX, CNAME, TXT, NS, and SOA records for troubleshooting email, hosting, and DNS.
  • WHOIS Lookup — Look up domain registration details: registrar, dates, and status for research and due diligence.
  • IP Address Lookup — Resolve IPv4 or IPv6 to geolocation, ISP, ASN, and hostname for network and fraud analysis.
  • Domain Age Checker — See how long a domain has been registered—useful for SEO trust signals and quick vetting.
  • Robots.txt Checker — Fetch and review robots.txt rules, directives, and sitemap lines to catch crawler misconfiguration.
  • Meta Tags Extractor — Extract title, meta description, Open Graph, Twitter Card, and canonical tags from any live URL.
  • Open Graph Preview — Preview how a link may appear when shared on social networks before you publish or pitch.

Frequently asked questions

What does this SSL certificate checker show?
Enter a public domain or HTTPS URL. We open a TLS connection to the host (default port 443 unless you specify another in the URL), read the server certificate chain, and report validity dates, issuer, subject, Subject Alternative Names (SANs), fingerprints, TLS protocol version, and whether the chain validates against public trust stores on our server.
Why does HTTP URL still check port 443?
TLS certificates protect HTTPS traffic. If you paste http://example.com without a port, we still probe example.com on port 443 so you can inspect the certificate browsers use for HTTPS—even when the scheme you typed is plain HTTP.
Can I see expired or mis-issued certificates?
Yes. We connect with certificate validation relaxed so we can still display leaf and intermediate details. You will see expiry status and our server’s trust evaluation (authorized or not, plus the authorization error when validation fails).
Is this the same as browser padlock information?
It is similar: you see the same certificate fields browsers use (names, dates, issuer). Browsers may cache pins, use CT logs, or apply enterprise policies, so always confirm critical changes in your target browsers and operating systems too.
Do you store domains or certificate data?
The check runs on demand for troubleshooting. Treat this as a quick operational signal, not a compliance audit log. Avoid entering sensitive internal hostnames; private IPs and local names are blocked.
What is a certificate chain?
Servers usually send a leaf certificate for your domain plus one or more intermediate certificates that link to a root trusted by clients. A broken or incomplete chain can cause warnings even if the leaf certificate is valid.
What are Subject Alternative Names (SANs)?
SANs list hostnames the certificate is valid for (for example www.example.com and example.com). Modern HTTPS relies on SANs; the legacy Common Name (CN) alone is not enough for every client.
How often should I check TLS expiry?
Most teams monitor automatically (APM, uptime, or certificate managers). For manual checks, review production hosts after any migration or CDN change and at least monthly for smaller sites. Combine this tool with DNS and redirect checks from our website utilities for fuller coverage.