Inspect TLS/SSL certificates on any domain. Check expiration dates, Certificate Authority (CA) trust chains, subject alternative names (SAN), and protocol support.
The padlock in a browser depends on a valid TLS/SSL certificate, and a certificate that is expired, misconfigured or issued for the wrong name will break trust — often with an alarming warning that drives visitors away. This tool inspects the certificate a domain presents and reports the essentials: when it expires (with a countdown), who issued it, which names it covers through its Subject Alternative Names, and which protocol versions are supported.
Expiry is the most common failure, because certificates are valid only for a limited period and a missed renewal takes a site offline for secure connections. Checking the trust chain matters too: a certificate must link back to a recognised Certificate Authority, and a broken or incomplete chain can cause failures on some devices even when it looks fine on others. Confirming the SANs ensures every hostname you serve — apex and www, for instance — is actually covered.
Run this before a certificate is due to expire, after any change to your TLS setup, and when diagnosing a browser trust warning. It is a fast way to confirm that visitors will get a clean, secure connection rather than a scary error page.
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