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Certificate Decoder

Decode and inspect PEM-encoded SSL/TLS certificates and CSRs. View validity periods, subject alternative names (SAN), issuer details, and public key information.

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aboutTool

Certificate Decoder decodes PEM-formatted SSL/TLS certificates into a human-readable format, showing expiry dates, issuers, and domain identities.

howToUse

  1. Paste the text starting with -----BEGIN...
  2. Click the Decode button
  3. Carefully review the common name, SANs, and validity dates

features

  • Full X.509 standard certificate parsing
  • Extraction of Subject Alternative Names (SAN)
  • Issuer (CA) and signature algorithm details
  • Calculated remaining validity period
  • Secure local processing for sensitive files

faq

Do I need my private key?

No, never share or paste your private key here; only public certificates and CSRs are needed.

How can I check expiry?

The decoder will prominently display the "Not After" date showing exactly when the certificate expires.