🔐 Certificate CRT Decoder
Decode and analyze X.509 SSL/TLS certificates. Extract detailed information from CRT, PEM, or CER certificate files including validity dates, issuer details, subject information, and public key data. All processing is done locally in your browser.
📄 Certificate Input
Supported: .crt, .cer, .pem, .der (PEM or binary DER, single certificate or full chain)
📋 Decoded Certificate
Decoded certificate information will appear here...
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About Certificate CRT Decoder
This tool helps you decode and analyze X.509 SSL/TLS certificates in various formats. Simply paste your certificate or upload a file to extract comprehensive information about the certificate.
Features:
- Multiple Format Support: Works with PEM, CRT, CER, and other common certificate formats
- Complete Certificate Details: View version, serial number, signature algorithm, and more
- Issuer & Subject Info: Extract detailed information about certificate issuer and subject
- Validity Period: Check certificate validity dates and expiration status
- Public Key Information: View public key algorithm, size, and modulus
- Extensions: Decode every extension: Extended Key Usage (Server / Client Authentication, Code Signing, S/MIME…), Subject Alternative Names, Key Usage, Basic Constraints, AIA (OCSP), CRL Distribution Points, Certificate Policies (DV/OV/EV), Certificate Transparency SCTs, OCSP Must-Staple, with critical flags
- Purpose Summary: See at a glance what the certificate can be used for (server, client, email, code signing…) and whether it is a CA or self-signed
- Fingerprints: SHA-256, SHA-1 and SPKI pin (base64)
- Certificate Chains: Paste a full chain (fullchain.pem) and every certificate is decoded
Supported Certificate Formats:
- PEM: Base64 encoded certificates with BEGIN/END markers
- CRT: Common certificate file format (usually PEM encoded)
- CER / DER: Binary DER certificates are detected and converted automatically
Common Use Cases:
- Verify certificate details before installation
- Check certificate expiration dates
- Validate issuer information
- Inspect Subject Alternative Names (SANs)
- Debug SSL/TLS certificate issues
- Extract public key information
- Check whether a certificate allows Client Authentication (mTLS, VPN, 802.1X)
Privacy & Security:
All certificate decoding is performed entirely in your browser using JavaScript. No certificate data is transmitted to any server, ensuring complete privacy and security of your sensitive information.