X.509 Certificate Decoder

Decode TLS certificates, expiry, SANs, and fingerprints locally

Decode X.509 PEM or DER certificates — subject, issuer, SANs, validity, and fingerprints, all in your browser.

Also known as: decode x509 · certificate inspector · parse pem certificate · ssl cert decoder

100% In-Browser & Private — your data never leaves this device
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How to use the X.509 Certificate Decoder

  1. Paste a PEM certificate block or load a .pem / .crt file.
  2. Review subject, issuer, validity window, SANs, and key info.
  3. Copy fingerprints (SHA-256) for pinning or inventory checks.

FAQ

Can I decode certificate chains?
Paste multiple PEM blocks to inspect each certificate in the chain separately.
Is my certificate uploaded?
No. Parsing uses the Web Crypto API and runs entirely in your browser.
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