X.509 Certificate & CSR Decoder (Private & Secure)
Decode and inspect X.509 SSL/TLS certificates and CSR requests in your browser. View subject and issuer, expiry dates, public key details, and SHA-256/SHA-1 fingerprints.
How to use
- Paste a PEM certificate (-----BEGIN CERTIFICATE-----) or CSR (-----BEGIN CERTIFICATE REQUEST-----), or click 'Upload Certificate' to load a PEM-encoded .pem/.crt/.cer/.csr file.
- Instantly inspect the Valid/Expired badge, Not Before/Not After dates, Subject CN, and Issuer CN.
- Review Public Key Info (algorithm, key size), the signature algorithm, serial number, and SHA-256/SHA-1 fingerprints.
Technical Considerations
- Expired certificates are flagged with an Expired badge.
- Wildcard Common Names (e.g. *.example.com).
Keyboard Shortcuts
- Ctrl/Cmd + KOpen Command Palette
100% Client-Side Privacy: This tool executes entirely within your browser's runtime environment. No payloads, tokens, or inputs are transmitted to external servers.