Free PKI tool

Free Certificate Decoder — read any X.509 certificate instantly

Paste a PEM-encoded certificate to see its issuer, subject, validity window, Subject Alternative Names, key usage, extensions, and fingerprint — without OpenSSL or an online upload.

Open in full-page tool suite →

How it works

Three steps, nothing leaves your browser

Paste the certificate

Copy the full PEM block, including the BEGIN/END CERTIFICATE lines.

Read the decoded fields

Issuer, validity dates, SANs, key usage, and fingerprint appear immediately.

Spot problems early

Catch an expired, mismatched, or wrong-domain certificate before it causes an outage.

Questions

Common questions

What certificate formats does this support?

Standard PEM-encoded X.509 certificates (the -----BEGIN CERTIFICATE----- format).

Can I decode a certificate chain?

Paste the leaf certificate here for full details; use the Bulk Decoder or Chain Sorter tool for multi-certificate chains.

Is this safe for certificates I haven't deployed yet?

Yes — nothing is uploaded, decoding happens entirely in your browser.