historia.vg / Tools / X.509

X.509 Certificate Decoder

Paste a PEM certificate, a whole chain, or base64 DER. Certificates are decoded automatically below. Everything stays in your browser; signatures and trust are not verified.

CLI alternative

Decode a PEM certificate with OpenSSL. Add -inform DER for binary DER input.

openssl x509 -in cert.pem -text -noout

Install:

sudo pacman -S openssl
sudo apt install openssl