Paste a PEM-encoded X.509 certificate to decode and inspect all fields: subject, issuer, validity period with expiry status, public key algorithm and size, Subject Alternative Names, key usage, extended key usage, extensions, and SHA-256/SHA-1 fingerprints. Supports certificate chains with tabbed navigation. Drag and drop .pem, .crt, or .cer files. Detects and warns about private keys. Pure JavaScript ASN.1 parser — all decoding runs in your browser.