SSL & X.509 Certificate Decoder

Decode and inspect X.509 SSL/TLS certificates locally. View Subject, Issuer, Validity expiration countdown, SANs, serial numbers, and SHA-256 fingerprints.

Paste PEM Certificate or Upload .crt / .pem / .cer

Embed this tool on your website / blog No code required · Copy and paste

<iframe src="https://lucentool.com/certificate-decoder" width="100%" height="650" style="border:1px solid #e5e0d8;border-radius:12px;max-width:850px;width:100%;" frameborder="0"></iframe>
<div style="font-size:12px;color:#78716c;margin-top:6px;font-family:sans-serif;">Powered by <a href="https://lucentool.com/certificate-decoder" target="_blank" style="color:#c85a32;text-decoration:none;">Lucentool - SSL & X.509 Certificate Decoder</a></div>

HTML Embed Code (iframe):

<iframe src="https://lucentool.com/certificate-decoder" width="100%" height="650" style="border:1px solid #e5e0d8;border-radius:12px;max-width:850px;width:100%;" frameborder="0"></iframe>
<div style="font-size:12px;color:#78716c;margin-top:6px;font-family:sans-serif;">Powered by <a href="https://lucentool.com/certificate-decoder" target="_blank" style="color:#c85a32;text-decoration:none;">Lucentool - SSL & X.509 Certificate Decoder</a></div>

What is an X.509 SSL/TLS Certificate?

X.509 (RFC 5280) is the standard format for public key certificates used globally across TLS/SSL, HTTPS, and email encryption. It binds an identity to a public key signed by a trusted Certificate Authority (CA).

Offline Privacy for Corporate & Internal Certificates

When troubleshooting mTLS, self-signed internal endpoints, or certificate chain validation errors, developers without OpenSSL installed often paste certificates into random online tools. This leaks internal hostnames, corporate structure, and public key fingerprints. Lucentool runs 100% in local memory with zero external requests.

SSL & X.509 Certificate Decoder

What is an X.509 SSL/TLS Certificate?

Offline Privacy for Corporate & Internal Certificates

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