Checking an expiry date at a glance
A server certificate's PEM block
Subject, issuer, validity dates and an expired badge if notAfter has already passed.
Certificate / CSR Decoder
Decode a PEM-encoded X.509 certificate or CSR and see its subject, issuer, validity and SANs.
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About this tool
A PEM-encoded certificate or CSR is a base64 blob of ASN.1 by design — unreadable until something parses it. This decodes either one entirely client-side and shows what's actually inside: subject, issuer, validity window, subject alternative names, key size.
How to use it
- Paste a PEM block — a certificate (-----BEGIN CERTIFICATE-----) or a certificate signing request (-----BEGIN CERTIFICATE REQUEST-----).
- Press Decode to see its fields, expiry status and alternative names.
Examples
Common problems
- It says the PEM is invalid, but the file opens fine elsewhere.
- Make sure the full block was pasted, including the -----BEGIN----- and -----END----- lines with no extra characters before or after — a truncated paste is the most common cause.