Instantly verify SSL/TLS certificates for any domain. Check expiry dates, issuer details, Subject Alternative Names, certificate chain, key strength, and get an overall security grade.
An SSL certificate checker connects to a domain on a specified port (default 443), completes a TLS handshake, and extracts all the metadata from the server's certificate. This includes the certificate's expiry date, the Certificate Authority (CA) that issued it, the domains it covers (SANs), the cryptographic key type and strength, and the full certificate chain back to the root CA.
This tool performs a live, real-time check — it contacts the actual server each time, so you always get the current certificate, not a cached result.
Why SSL Certificate Monitoring Matters
Expired certificates cause browsers to show a full-page security warning, immediately destroying user trust and search rankings.
Misconfigured chains can cause failures on mobile devices and older clients even if the cert itself is valid.
Weak key sizes (RSA < 2048-bit) are rejected by modern browsers and CA/Browser Forum standards.
SHA-1 signatures are deprecated — any cert signed with SHA-1 is rejected by Chrome, Firefox, and Safari.
Wildcard vs SAN coverage — verify your cert actually covers all the subdomains your site uses.
Frequently Asked Questions
A Subject Alternative Name (SAN) is an extension that lets a single SSL certificate cover multiple domain names. For example, a cert might cover example.com, www.example.com, and api.example.com all at once. Modern certificates use SANs instead of (or in addition to) the Common Name field.
SSL certificates form a chain of trust: your server's certificate is signed by an Intermediate CA, which is signed by a Root CA. Browsers trust the Root CA (pre-installed), and verify the chain downward. If any intermediate cert is missing from the chain your server sends, some clients will reject the connection even though the end certificate is valid.
If using Let's Encrypt, run `certbot renew` on your server. For paid certs, purchase a renewal from your CA and re-issue. Then install the new cert on your web server (Apache, Nginx, etc.) and reload the server. The entire process takes 5–15 minutes with Let's Encrypt.
DV (Domain Validated) only confirms domain ownership — fastest and cheapest (Let's Encrypt). OV (Organisation Validated) also verifies the legal organisation — better for businesses. EV (Extended Validation) involves the most thorough vetting and historically showed a green bar in browsers, though most browsers have removed the visual distinction. For most websites, DV is sufficient.
Yes — change the port number in the port field next to the domain input. Common SSL ports include 443 (HTTPS), 465 (SMTPS), 636 (LDAPS), 993 (IMAPS), 995 (POP3S), and 8443 (alternative HTTPS). The checker will attempt a TLS connection on whatever port you specify.