CSR Decoder
Paste a CSR to inspect its subject, SANs, key type, and requested extensions.
Frequently asked questions
What is a CSR and why decode it?
A Certificate Signing Request (CSR) contains your public key and the subject details you send to a Certificate Authority. Decoding it lets you verify the domain, SANs and key type are correct before you submit, avoiding a mis-issued certificate.
What details does the CSR decoder reveal?
It shows the subject (Common Name and organisation fields), the public key algorithm and size, the signature algorithm, and any Subject Alternative Names, plus whether the request includes a wildcard hostname.
Does decoding a CSR expose my private key?
No. A CSR only carries your public key and subject information — the private key never leaves your server and is not part of the CSR. Decoding is safe, and this page runs browser-only with no tracking or storage.
My CSR is missing SANs — is that a problem?
Modern certificates rely on the Subject Alternative Name list, not just the Common Name. If required hostnames are missing from the SANs, the issued certificate will not be valid for them, so regenerate the CSR with every hostname included.
What key type should my CSR use?
RSA 2048 is universally compatible; ECDSA P-256 is faster and more compact with equivalent security. Confirm your Certificate Authority and clients support your choice before issuing.