Paste any PEM certificate to extract subject, issuer, validity dates, serial number, SANs, and signature algorithm.
Pure client-side ASN.1 DER parsing. Supports RSA and ECDSA. Works with leaf certs, intermediates, and root CAs.
Decodes PEM-encoded X.509 certificates and displays the certificate details: subject, issuer, validity period, subject alternative names (SANs), key algorithm and size, signature algorithm, extended key usage, and basic constraints.
Paste a certificate in PEM format (the block starting with -----BEGIN CERTIFICATE-----) and the tool extracts all fields in readable form.
Certificate review is useful during TLS configuration audits, when troubleshooting certificate errors, and when validating that a certificate matches expected parameters before deployment. SANs reveal all hostnames covered by the certificate.
Common findings in certificate reviews: SHA-1 signatures (deprecated), weak key sizes (RSA 1024), overly broad wildcard coverage, certificates issued by unexpected CAs, and expiration dates in the near future that will cause outages if not renewed.