The SSLFOR SSL Decoder turns PEM certificate and CSR data into readable fields. For certificates it shows the X.509 version, serial number, subject, issuer, validity period, RSA key size, signature OID, Subject Alternative Names and SHA-256 fingerprint.
For a CSR, the decoder verifies the request signature, shows the subject, public-key size and any SAN extension request.
Decoding is useful before installation, during renewal review, or when comparing what was requested in a CSR with what a certificate authority actually issued.