Certificate Decoder

Decode PEM or DER certificates locally. Inspect subject, SANs, issuer, expiry and SHA-256 public-key pin. Copy details or download JSON.

How to use Certificate Decoder

Paste one PEM certificate or select a PEM/DER certificate file. Use a separate decode for each certificate in a chain.

Understanding the results

Review subject, issuer, serial number, validity dates, public key and extensions. Unknown extension values are shown as encoded hex. Being within validity dates does not mean a certificate is trusted; signatures, chain trust and revocation are not checked.

Does this check the certificate currently served by a website?

No. Use SSL Certificate to inspect a live website. Certificate Decoder inspects the file or text you provide.

What is the difference between a certificate decoder and an SSL checker?

The decoder inspects a certificate you paste or open locally, including its SHA-256 public-key pin. The SSL checker connects to a website and inspects the certificate that website currently presents.