SSL/CSR Decoder

100% Client-Side

Encrypted Input

Paste Certs, CSRs, or JSON secrets. Auto-detects bundles.

Decoded Details

Awaiting valid certificate, CSR, or bundle...

Frequently Asked Questions

What does the Expert Web Tools SSL/CSR Decoder do?
It is a fully client-side utility that parses Base64 PEM-encoded X.509 SSL certificates and PKCS#10 Certificate Signing Requests (CSRs). It extracts standard details (Common Name, Validity, Issuer, SANs, EKUs) and supports advanced features like multi-certificate bundle parsing and local Private Key matching.
Why doesn't my CSR show Subject Alternative Names (SANs)?
SANs are requested extensions. If you generated a CSR without explicitly passing SAN configuration flags to OpenSSL or your generation tool, they will not be included. Furthermore, even if you include them, the Certificate Authority (CA) makes the final decision on which SANs are actually included in your final issued certificate.
What certificate and key formats are supported?
The decoder supports standard PEM-encoded formats (starting with -----BEGIN CERTIFICATE----- or -----BEGIN CERTIFICATE REQUEST-----). It robustly handles both traditional RSA algorithms and modern Elliptic Curve Cryptography (ECDSA) keys such as secp256r1.
Does this tool decrypt PKCS#12 (.pfx or .p12) archives?
No. To maintain a strict privacy and security posture, this tool only processes plaintext PEM files. It does not decrypt binary archives or encrypted private keys (e.g., keys requiring a passphrase).
Is it safe to decode SSL Certificates and CSRs online?
Yes. Expert Web Tools processes all SSL, CSR, and Private Key data 100% locally in your browser using JavaScript. Your sensitive infrastructure secrets never leave your device and are never logged or uploaded to any server.
How do I check if my Private Key matches my SSL Certificate?
Simply paste your SSL Certificate (or CSR) in the top input box, check the "Verify Private Key Match" toggle, and paste your Private Key in the bottom box. Our tool instantly calculates the modulus and public key curve of both files locally to confirm if they are a mathematically valid cryptographic pair.
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