Decode a Certificate Signing Request (CSR)
Paste a Certificate Signing Request (CSR, PKCS#10 format) in PEM format to extract the subject (CN, organization, country...) and the associated public key information, before submitting it to a certificate authority. The ASN.1/DER decoding is done entirely in your browser.
How it works
A CSR (Certificate Signing Request) is a file in PKCS#10 format, encoded in ASN.1/DER and then wrapped in Base64 (PEM format). This tool implements a small generic ASN.1 parser, then navigates the standard CSR structure (CertificationRequestInfo) to extract the subject (Name, a series of attribute/value pairs like CN, O, C) and the associated public key information (algorithm and approximate size), without ever having to send the CSR to a server.
Why check a CSR before sending it to a certificate authority?
A certificate authority (CA) will issue a certificate that exactly matches the subject contained in the CSR: a capitalization error, a misspelled domain in the CN, or an incorrect organization field will only be detected after the fact, sometimes forcing you to regenerate a new request. Reviewing the decoded subject lets you catch this type of error before sending it.
Does this decoder verify the cryptographic validity of the CSR?
No: it only reads the structure and displays its declared content (subject, key algorithm). It does not verify the CSR signature (which proves that the requester actually owns the corresponding private key) — this verification is performed by the certificate authority when issuing the certificate.
Privacy: the pasted CSR is decoded 100% locally in your browser — it is never sent to a server. A CSR does not contain a private key, but it may still contain organizational information you might not want to share unnecessarily.