AV-S12
X.509 Certificate Decoder
Decode a certificate or CSR: subject, issuer, validity, SANs, key usage, extensions and fingerprints.
● Runs on your device; nothing is uploadedHow to use it
- Paste a PEM certificate or CSR, or Base64 DER, into the box.
- Or drop a .pem, .crt, .cer, .der or .csr file.
- Read the subject, issuer, validity status, SANs and key usage.
- Copy fingerprints, the serial or the PEM as needed.
Limits
- File size
- 1 MB
Features
- X.509 certificates and PKCS#10 certificate signing requests
- Validity status with days left or days since expiry
- SHA-256, SHA-1 and SPKI SHA-256 fingerprints
- Named key usage, extended key usage and basic constraints
- Lists all extensions with critical flags
For AI agents: avtools_x509_decoder
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