SSL Certificate Checker

Check the SSL/TLS certificate for any domain. See issuer, validity dates, expiry countdown, SANs, and protocol version.

How to Check an SSL Certificate

Enter a domain name (without https://) and click Check SSL. The tool connects to the domain on port 443, retrieves the SSL/TLS certificate, and displays detailed information including the certificate issuer (e.g., Let's Encrypt, DigiCert), subject (the domain the cert was issued for), validity period, days remaining until expiry, Subject Alternative Names (SANs), serial number, and TLS protocol version. A color-coded expiry badge makes it easy to see at a glance whether the certificate is valid, expiring soon, or already expired.

Why SSL Certificates Matter

SSL/TLS certificates encrypt the connection between a browser and your server, protecting sensitive data like passwords and payment information. Google uses HTTPS as a ranking signal, so sites without SSL may rank lower. Expired certificates cause browser warnings that drive visitors away — studies show that over 80% of users will leave a site after seeing a certificate error. Monitoring certificate expiry is critical for maintaining uptime and trust. Free certificates from Let's Encrypt are valid for 90 days and must be renewed regularly. This tool helps you verify that renewals are working and certificates are correctly configured.

Frequently Asked Questions

This is the number of days until the certificate expires. Certificates should be renewed well before expiry — Let's Encrypt recommends renewing at 30 days remaining. If the number is negative, the certificate has already expired.

SANs list all the domains and subdomains a certificate is valid for. A certificate for example.com might also include www.example.com, api.example.com, etc. The browser checks that the domain you're visiting matches one of the SANs.

A self-signed certificate is one where the issuer and subject are the same entity, rather than being signed by a trusted Certificate Authority. Browsers do not trust self-signed certificates and will show a warning. They should only be used for development and testing.

TLS 1.3 is the latest and most secure version. TLS 1.2 is still considered secure. TLS 1.0 and 1.1 are deprecated and should be disabled. This tool shows which TLS version was negotiated during the connection.

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