SSL Checker

Enter a domain name above and click "Check SSL" to inspect the certificate.

About SSL Checker

SSL Checker inspects the TLS/SSL certificate of any domain: issuer, subject, validity period, expiry date, Subject Alternative Names (SANs), certificate chain, and key algorithm. Use it to verify certificates before deployment, monitor upcoming expirations, debug HTTPS configuration issues, and confirm that the right certificate is being served.

How it Works

1Enter the domain name (e.g. example.com) and click Check.
2The tool queries the domain's SSL endpoint via the SSL Labs API.
3Certificate details are returned: issuer, validity dates, SANs, chain, and grade.
4Expiry warnings are shown if the certificate expires within 30 days.

Frequently Asked Questions

How do I know if my SSL certificate is about to expire?

The tool displays the 'Valid Until' date and flags certificates expiring within 30 days in amber and within 7 days in red. For automated monitoring in production, set up a cron job with openssl s_client or use a monitoring service like UptimeRobot or Cronitor which send email/Slack alerts on expiry.

What are Subject Alternative Names (SANs)?

SANs are additional domain names and IP addresses that a single certificate covers. A SAN certificate for example.com might also cover www.example.com, api.example.com, and *.example.com (wildcard). Modern certificates always use SANs; the older CN-only approach is deprecated by all major browsers.

What is certificate chain validation?

A certificate chain is the sequence from your server's certificate to the root CA certificate. Each certificate is signed by the one above it. If an intermediate certificate is missing or mis-ordered in the server's configuration, some clients (especially older mobile devices) will fail to validate the certificate and show security errors, even though the leaf certificate itself is valid.

What does TLS 1.3 mean and should I use it?

TLS 1.3 is the latest version of the Transport Layer Security protocol (2018). It is faster than TLS 1.2 (requires only one round-trip for the handshake vs two), drops legacy cipher suites, and provides better forward secrecy. All major browsers support it. TLS 1.0 and 1.1 are deprecated — servers that only support these will fail validation in modern browsers.

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Frequently Asked Questions