SSL Certificate Checker

SSL Certificate Checker opens a real TLS handshake to a domain on port 443 (or any port you choose) and reports back exactly what the server presented: the leaf certificate, its issuer, the validity window, the days remaining, the Subject Alternative Names list, the full chain back to the root, the negotiated TLS protocol version, and the negotiated cipher suite. The check runs server-side because browsers don't expose the raw certificate to JavaScript. We use Node's TLS stack with rejectUnauthorized turned off so we can show you details for self-signed and untrusted certs too — the trust verdict is reported separately so you can see "yes, the cert is valid, but not trusted by Node's CA store" as distinct facts. The expiry badge turns red below 14 days remaining and amber below 30, so a glance tells you whether something needs attention. The SAN list is the source of truth for which hostnames the cert actually covers — easy to forget to add a new subdomain when re-issuing. Common use cases: confirming a freshly-renewed cert is actually serving; auditing the SAN list before re-issue; checking a self-signed cert in a staging environment; spotting weak cipher suites; verifying TLS 1.3 is negotiating where you expect.