CSR Decoder
Decode a Certificate Signing Request (CSR) and inspect its contents: Subject (CN, organization, location), public key (type & size), Subject Alternative Names (SAN), signature algorithm and signature verification. Your CSR is parsed locally and never stored.
What is a CSR?
A CSR (Certificate Signing Request) is an encoded request you send to a Certificate Authority (CA) when applying for an SSL/TLS certificate. It contains your public key and identity details (domain, organization, country), signed with the matching private key.
What does a CSR contain?
- Subject — Common Name (the domain), Organization (O), Organizational Unit (OU), Locality (L), State (ST), Country (C), email.
- Public key — the type (RSA, EC) and size (e.g. 2048-bit).
- Subject Alternative Names (SAN) — additional domains the certificate will cover.
- Signature — the algorithm (e.g. SHA-256 with RSA) and the digital signature of the request.
What does this tool do?
Paste your CSR — the entire block from -----BEGIN CERTIFICATE REQUEST----- to -----END CERTIFICATE REQUEST----- — and the tool decodes all of the fields above. It also confirms the CSR signature is valid and warns you if the key is too small (e.g. RSA below 2048-bit).