Reads a PEM or DER-encoded X.509 certificate and decodes its subject, issuer, validity dates, public key info and Subject Alternative Names directly from the ASN.1 structure.
Checking exactly what a certificate says — who it's for, who issued it, when it expires, what domains it covers — without a browser's cert inspector or the openssl CLI.
Drop a .pem, .crt, .cer or .der file. Subject, issuer, validity, public key and SANs all appear immediately.
Decodes the ASN.1/DER structure directly — it doesn't verify the signature or check it against any trust store.