SSL Certificate Checker

Check whether a site's SSL/TLS certificate is valid, when it expires, who issued it and which domains it covers.

What the SSL certificate check shows

The tool connects to the domain over TLS and reads the certificate the site uses to prove its identity. You immediately see whether the certificate is currently valid, when it expires and how many days are left. It also shows the issuer (the certificate authority, such as Let's Encrypt, DigiCert or Sectigo) and the SAN list: every hostname the certificate covers, including subdomains like www. That is handy after moving a site to a new server, when you need to confirm HTTPS is being served correctly.

What happens when a certificate expires, and how to renew

As soon as a certificate expires, browsers show a full-page security warning and most visitors close the tab before reaching your content. Traffic drops, checkout forms break and API integrations reject the untrusted connection. The reliable fix is automatic renewal rather than manual renewal: free Let's Encrypt certificates last 90 days, and certbot or your control panel (cPanel AutoSSL, Plesk) renews them on a schedule, typically 30 days before expiry. Most managed hosting plans include free SSL with auto-renewal.

What to check when the browser shows a security warning

A warning does not always mean the certificate expired. There are several causes, and this tool helps tell them apart.

  • Expired: the end date is in the past; reissue the certificate or fix auto-renewal.
  • Name mismatch: you opened an address that is not in the SAN list (a common case: the certificate covers example.com but you visited www.example.com).
  • Self-signed: the issuer is not a trusted authority; such certificates are only suitable for testing.
  • Mixed content: the certificate is fine, but the page loads some resources over plain HTTP and the padlock disappears.

Frequently asked questions

How do I find out how many days are left on a certificate?
Enter the domain and the tool shows the expiry date and the exact number of days remaining. Renew two to four weeks before the end date.
What is the SAN field in a certificate?
It lists every domain and subdomain that one certificate protects. If your address is not in the list, the browser reports a name mismatch.
Why does the browser show a warning if the certificate has not expired?
The cause may be a name mismatch, a self-signed certificate or mixed content. Check that the address is in the SAN list and that all page resources load over HTTPS.
Do I need to renew a Let's Encrypt certificate manually?
No. It is issued for 90 days and renewed automatically by certbot or your control panel. Manual renewal is only needed if the automation fails.
What is a self-signed certificate?
It is a certificate issued without a trusted certificate authority. It encrypts traffic, but browsers do not trust it, so it is not suitable for a public website.
Does an expired certificate hurt search rankings?
Indirectly, yes: visitors leave the warning page in large numbers, and search engines take HTTPS and site accessibility into account.