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How to check an SSL certificate

Review certificate validity, identity, and expiration for a public HTTPS site.

The short answer

Enter the domain in an SSL checker and confirm three things: the certificate is trusted, it covers the exact hostname, and its expiry date is not close.

Use the free SSL Certificate CheckerUse the free Headers CheckerUse the free Website Score Checker

Step by step

  1. Open SSL Checker and enter the domain (for example example.com).
  2. Check the status: Valid, or the specific problem found.
  3. Review days until expiry, issuer, and the covered hostnames (SAN list).
  4. Look at the chain: a missing intermediate certificate is the most common cause of trust errors.
  5. Repeat for www and other subdomains you serve.

Technical details

  • The hostname must appear in the certificate's subject alternative names. Certificate validity does not by itself prove that every TLS setting is ideal.

Common mistakes

  • Checking the wrong hostname behind a redirect.
  • Confusing certificate expiry with domain registration expiry.
  • Ignoring intermediate certificate or client compatibility issues.

Limitations

  • A certificate check does not replace a full TLS configuration assessment of every protocol and cipher a server accepts.

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