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SSL Certificate Decoder

Paste a PEM-encoded SSL/TLS certificate to decode issuer, subject, validity dates, SANs, signature algorithm, and key details — entirely in your browser.

About SSL Certificate Decoder

The SSL Certificate Decoder reads PEM-encoded X.509 certificates and displays all key fields: issuer, subject, validity period, Subject Alternative Names (SANs), public key algorithm, signature algorithm, and serial number. Everything runs in your browser via the Web Crypto API — no certificate data is ever sent to a server.

How to Use

  1. Obtain the certificate in PEM format (begins with -----BEGIN CERTIFICATE-----).
  2. Paste it into the text area above.
  3. Click Decode Certificate to see all fields.

Frequently Asked Questions

Yes. All decoding happens in your browser. Your certificate is never uploaded or transmitted anywhere.

The tool accepts PEM format — a base64-encoded certificate wrapped in -----BEGIN CERTIFICATE----- and -----END CERTIFICATE----- headers.