Certificate Decoder

Decode X.509 SSL/TLS certificates (PEM, DER, CRT, CER). View Subject Alternative Names (SANs), expiration dates, and key details.

Privacy First: 100% Client-Side Parsing. Your certificate never leaves your computer. All cryptographic parsing is done locally in your browser via JavaScript. No backend servers are involved.

Paste Certificate (PEM or Base64)

— OR —

Click to Upload or drag & drop a file
Supports .pem, .crt, .cer, .der

Certificate Details

Subject (Common Name)

Issuer

Valid From

Valid To

Status

Subject Alternative Names (SANs)

Key Algorithm

Serial Number

SHA-256 Fingerprint

SHA-1 Fingerprint