About the SSL Certificate Checker
This SSL checker connects to a domain on port 443, as a browser would, and shows the TLS certificate it receives: the valid-from and expiry dates with days remaining, the issuing certificate authority, the subject alternative names (the hostnames the certificate covers), whether the hostname matches, the certificate chain, key type and the TLS protocol negotiated.
An expired certificate, a missing intermediate in the chain or a certificate that does not cover www or a subdomain causes browser warnings that drive visitors away and can stop search engines crawling HTTPS pages. Public certificate lifetimes are being shortened in stages from 2026, so automated renewal, through your host or a tool using ACME such as Let's Encrypt, is increasingly important. The check uses only the public connection.
How to use it
- Enter the domain or subdomain, such as www.example.com.
- Check the expiry date and days remaining.
- Confirm the hostname matches and the chain is complete.
- Renew or reissue the certificate if anything fails.
Frequently asked questions
What does an incomplete certificate chain mean?
Browsers need to link your certificate to a trusted root through one or more intermediate certificates. If the server does not send the intermediates, some browsers and tools show errors even though the certificate is valid. Install the full chain provided by your certificate authority.
Does my certificate cover www and non-www?
Only if both hostnames appear in the subject alternative names. Look at the SAN list in the results. If one is missing, visitors to that version will see a warning, so reissue the certificate with both names or use a wildcard where appropriate.
Does HTTPS help SEO?
Google has confirmed HTTPS is a lightweight ranking signal. More importantly, browsers mark HTTP pages as not secure and show errors for invalid certificates, which can stop visitors from reaching your site at all. Keeping a valid certificate on every hostname, including www and subdomains, avoids those problems and keeps HTTPS working everywhere.