Certificate Decoder

Inspect PEM or DER certificate format and DER byte information locally.

Local processingNo input storage

Inspect certificate fields

Paste a PEM or Base64 DER certificate to read its subject, issuer, validity period, and host names.

Everything is computed in this browser and never sent to a server.

PEM certificate or Base64 DER

Paste a certificate to list its subject, issuer, validity period, and host names.

This tool parses format only. It does not determine trust, chain integrity, revocation, or hostname validity.

How to use

Paste a PEM certificate or Base64 DER data to inspect its format and size.

Privacy

No. Website validation needs trusted roots, chain, hostname, and revocation checks.

Limits and guidance

Never paste a private key into a tool. This is not a PKI trust verifier.