X.509 Certificate Decoder

Inspect PEM or DER X.509 certificates.

PEM or DER (hex) certificate

Certificate parsing runs entirely in your browser. The private key is never needed — only the public certificate is decoded.

About this tool

Paste a Base64-encoded PEM certificate or hex DER and decode every field — subject, issuer, validity, SANs, key usage, extensions and fingerprint — nothing leaves your browser.

It runs completely in your browser — no input is sent anywhere, and this page loads no ads or third-party scripts, so it is safe to use with data you would not paste into a hosted service.

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