Paste a PEM-encoded certificate (e.g. from a .crt or .pem file) and view decoded information: subject, issuer, and validity dates.
About Certificate (PEM) Decoder
X.509 certificates are often stored in PEM format (base64 between -----BEGIN and -----END). This tool decodes the certificate and displays subject, issuer, and validity. For debugging and DevOps. Runs in your browser.
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Is my certificate sent to a server?
No. Decoding happens entirely in your browser. The certificate never leaves your device.
What can I see from the certificate?
Subject (CN, O, etc.), issuer, validity (not before / not after), and optionally serial number. Full ASN.1 parsing would show more; this tool focuses on common fields.