Certificate Decoder

Decodes a PEM-encoded X.509 certificate and shows its subject, issuer, serial number, validity period, and signature algorithm. Paste a full certificate, including the BEGIN/END lines.

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Decodes a PEM-encoded X.509 certificate and shows its subject, issuer, serial number, validity period, and signature algorithm. Paste a full certificate, including the BEGIN/END lines.

Use cases

  • Checking who issued a certificate and when it expires
  • Verifying a certificate's subject matches the expected domain

Examples

A self-signed test certificate

-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----

{"subject": "CN=amigotoolz.test,O=AmigoToolz Test,C=US", "issuer": "CN=amigotoolz.test,O=AmigoToolz Test,C=US", "serial_number": "123456789", "not_valid_before": "2025-01-01T00:00:00+00:00", "not_valid_after": "2035-01-01T00:00:00+00:00", "signature_hash_algorithm": "sha256"}

FAQ

Is my data sent to a server?

Yes — the parsing runs on the server for this tool.

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