CSR File

What are CSR files and how to open them

Are you having problems opening a CSR file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your CSR files.

What is a CSR file?

A .CSR file is a Certificate Signing Request file.

A Certificate Signing Request (CSR) file, with extension .csr, is used in Public Key Infrastructure (PKI) systems when applying for an identity certificate. It is generated by someone who wants a certificate and contains information the Certificate Authority (CA) needs, including the public key of the requester and identification details such as name, organization, and domain. The CSR is signed with the requester's private key to prove ownership of the public key.

The process begins with generating a key pair (public and private keys). The public key plus the identifying details and optional attributes (such as certificate extensions or challenge passwords) are packaged into a data structure. The entire CSR is then digitally signed by the private key. A PKCS #10 (also called "Certification Request Syntax Specification Version 1.7") format is commonly used for CSRs. When the CA receives the CSR, it verifies the signature and the identity information, then issues the actual certificate (often in X.509 format) using the public key and supplied details.

On disk, many CSR files are stored in PEM format: Base64-encoded text bounded by "-----BEGIN CERTIFICATE REQUEST-----" and "-----END CERTIFICATE REQUEST-----" markers. Internally the data follows ASN.1 syntax, usually DER encoded before Base64 conversion.

Bytes at the file start usually match the ASCII string "-----BEGINCERTIFICATEREQUEST-----" (ignoring whitespace), and somewhere near the end the file includes "-----END CERTIFICATE REQUEST-----". This pattern helps programs detect that the file is a PEM-encoded CSR. (Byte signature data confirms this.)

How to open CSR files

We have identified one CSR opener that is compatible with this specific type of CSR file.

Programs that open Certificate Signing Request files

Last updated: August 5, 2026

Various apps that use files with this extension

These apps are known to open certain types of CSR files. Remember, different programs may use CSR files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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