How do I check if an SSL certificate is valid?

Enter a domain in the SSL Checker tool above. It connects to the server and checks certificate validity, expiration date, issuer, protocol version, chain length, and Subject Alternative Names (SANs).

What happens when an SSL certificate expires?

Browsers will show security warnings to visitors, which can block access to your site and damage trust. Expired certificates also hurt search rankings. Monitor certificates to renew them before expiration.

Is this SSL checker free?

Yes, the ServiceAlert.ai SSL Checker is completely free with no signup required. Enter any domain to instantly verify its SSL/TLS certificate status.

SSL Certificate Checker

Verify SSL/TLS certificates, check expiry dates, and view certificate details.

Quick Check Popular Domains

Free SSL Certificate Checker

SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) are cryptographic protocols that encrypt data between a user's browser and a web server. An SSL/TLS certificate authenticates a website's identity and enables secure HTTPS connections. Without a valid certificate, browsers display security warnings that erode user trust and hurt search rankings.

This free SSL checker lets you instantly verify any domain's certificate status. View the issuer, validity dates, days until expiry, protocol version, certificate chain length, and all Subject Alternative Names (SANs). Catch expiring certificates before they cause downtime or security warnings for your users.

Need Continuous Monitoring?

A one-time check is useful, but certificates can expire unexpectedly, especially when auto-renewal fails. ServiceAlert.ai monitors 695+ cloud services 24/7 and sends instant alerts via email, Slack, Teams, Google Chat, or Discord when outages occur — including SSL-related failures.

View current incidents or get started with free monitoring.