Certificate Decoder
Free online SSL certificate decoder. Paste a PEM certificate and instantly see all details including subject, issuer, validity dates, SANs, key size, signature algorithm, and fingerprints. Perfect for developers and sysadmins verifying certificate information before deployment. All decoding runs 100% client-side — your certificate never leaves your browser.
how to use
- 1.Paste your PEM certificate into the input box
- 2.Click Decode to inspect all certificate details
- 3.View subject, issuer, validity dates, SANs, and fingerprints
- 4.Use it to verify certificates before installing on your server
frequently asked
What certificate formats are supported?
Supports PEM format (-----BEGIN CERTIFICATE-----). If you have a DER binary file, use the PEM ↔ DER Converter tool first.
Is my certificate data secure?
Yes — all decoding happens entirely in your browser using the Web Crypto API. Your certificate is never sent to any server.
What information can I see?
Subject (CN, O, OU, C), Issuer, validity period (Not Before / Not After), Subject Alternative Names (SANs), public key info, signature algorithm, and SHA-1/SHA-256 fingerprints.