Files with the .CSR extension contains requests for signing a digital certificate, consisting of an encrypted text block containing data unambiguously identifying the applicant. The encrypted data contained in the request is the country, state, organization, domain, e-mail address, and public key.

Public and private keys are used to generate CSR files - the public key is saved in a file and the private key is used to sign a digital file. CSR files are used by the Certification Authority to confirm the identity of websites.