DevScratchpad

X.509 Certificate & CSR Decoder (Offline & Secure)

Decode and inspect X.509 SSL/TLS certificates and CSR requests in your browser. View Subject Alternative Names (SANs), expiry dates, fingerprints, and key usages.

How to use

  1. Paste a PEM certificate (-----BEGIN CERTIFICATE-----) or CSR (-----BEGIN CERTIFICATE REQUEST-----), or upload a .crt/.pem file.
  2. Instantly inspect certificate status, validity countdown, Common Name, and Issuer.
  3. Review Subject Alternative Names (SANs) and Cryptographic Properties (Key size, algorithm, SHA-256 fingerprint).

Technical Considerations

  • Expired or not-yet-valid certificates.
  • Wildcard DNS and multi-SAN SSL certificates.

100% Client-Side Privacy: This tool executes entirely within your browser's runtime environment. No payloads, tokens, or inputs are transmitted to external servers. Safe for offline usage.

Keyboard Shortcuts

  • Ctrl/Cmd + K — Open Command PaletteCtrl/Cmd + K — Open Command Palette

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