X.509 Certificate Decoder

Decode and inspect X.509 SSL/TLS certificates in PEM or DER format. View subject, issuer, validity, serial number, key usage, SANs, fingerprint, and raw ASN.1 structure. Fully client-side — your certificate never leaves your browser.

Paste a PEM certificate (including BEGIN/END CERTIFICATE lines) or upload a .pem/.der/.crt file:

Upload .pem/.der/.crt