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SSL Certificate Checker

Verify an SSL certificate: issuer, validity, expiry and covered domains.

What does an SSL checker do?

An SSL checker connects to a website over HTTPS and inspects its TLS certificate: whether browsers will trust it, who issued it, when it expires, which domain names it covers and which TLS protocol and certificate chain the server presents.

What the checks mean

  • Trusted certificate — the chain leads to a root certificate authority that browsers trust, and the certificate matches the domain. If not, visitors see a "Your connection is not private" warning.
  • Expiry — most certificates (like Let's Encrypt) last 90 days and renew automatically. Under 14 days left without renewal is a warning sign; expired certificates block visitors completely.
  • Domains covered (SAN) — every hostname the certificate is valid for. If www.example.com is missing, visitors to the www version get an error.
  • Protocol — TLS 1.2 or 1.3 are current; TLS 1.0/1.1 are obsolete.
  • Chain — server certificate, intermediate(s) and root. A missing intermediate causes errors on some devices.

Common SSL problems and fixes

ProblemFix
Expired certificateRenew, then check the auto-renew job (certbot timer, hosting panel)
Name mismatchIssue a certificate that includes every hostname you use, including www
Incomplete chainInstall the full chain (fullchain.pem), not just the certificate
Self-signed certificateReplace with a free certificate from Let's Encrypt or your host

HTTPS and SEO

HTTPS is a lightweight Google ranking signal and a must for trust — Chrome labels HTTP pages "Not secure". After switching, redirect all HTTP URLs to HTTPS with a single 301 (check with the Redirect Checker) and add an HSTS header (see the HTTP Headers Checker).

Frequently asked questions

How do I check if an SSL certificate is valid?

Enter the domain. The checker connects over HTTPS and shows whether the certificate is trusted, who issued it, when it expires and which domains it covers.

How long are SSL certificates valid?

Public certificates are valid for at most about 13 months, and many, such as Let's Encrypt, last 90 days with automatic renewal.

Why does my site show "Not secure"?

Either the page loads over HTTP, the certificate is invalid or expired, or the page loads some resources over HTTP (mixed content).

Is a free SSL certificate as good as a paid one?

For encryption, yes. Free domain-validated certificates from Let's Encrypt give the same browser padlock as paid DV certificates.

Does HTTPS help SEO?

Yes, slightly. HTTPS is a confirmed lightweight ranking signal and important for user trust.