Worked example
Check that the requested hostname appears in Subject Alternative Name and that the certificate has not expired.
Certificate Decoder
Decode X.509 SSL/TLS certificates (PEM, DER, CRT, CER). View Subject Alternative Names (SANs), expiration dates, and key details.
Privacy First: 100% Client-Side Parsing.Your certificate never leaves your computer. All cryptographic parsing is done locally in your browser via JavaScript. No backend servers are involved.
— OR —
How to use Certificate Decoder
Paste or upload a PEM, CRT, or DER certificate to inspect identity, SANs, issuer, validity, and fingerprints locally.
Common mistake
A successfully decoded certificate is not necessarily trusted; chain validation and hostname verification still matter.