Tools / CSR / certificate decoder

CSR / certificate decoder

Paste a PEM Certificate Signing Request or an X.509 certificate and read back exactly what's in it — before you hand the CSR to a CA, or to sanity-check what a CA issued.

Decodes

CSR: subject (CN, O, OU, L, ST, C, email), requested SANs, public key algorithm and size.
Certificate: subject and issuer, validity window and days remaining, SANs, key, signature algorithm (flags SHA-1), serial, SHA-256 / SHA-1 fingerprints.

Privacy

The PEM is parsed by openssl on our server and immediately discarded — nothing is stored, logged to disk, or sent to any certificate authority or third party. A CSR contains only a public key and your requested identity; it is safe to decode. Never paste a private key anywhere.