What is a CSR (Certificate Signing Request)?

What is a CSR? A CSR or Certificate Signing request is a block of encrypted text that is generated on the server that the certificate will be used on. It contains information that will be included in your certificate such as your organization name, common name (domain name), locality, and country. It also contains the public key that will be included in your certificate. A private key is usually created at the same time that you create the CSR.

A certificate authority will use a CSR to create your SSL certificate, but it does not need your private key. You need to keep your private key secret. What is a CSR and private key good for if someone else can potentially read your communications? The certificate created with a particular CSR will only work with the private key that was generated with it. So if you lose the private key, the certificate will no longer work.

What is contained in a CSR?

Name	Explanation	Examples
Common Name	The fully qualified domain name (FQDN) of your server. This must match exactly what you type in your web browser or you will receive a name mismatch error.	*.google.com mail.google.com
Organization	The legal name of your organization. This should not be abbreviated and should include suffixes such as Inc, Corp, or LLC.	Google Inc.
Organizational Unit	The division of your organization handling the certificate.	Information Technology IT Department
City/Locality	The city where your organization is located.	Mountain View
State/County/Region	The state/region where your organization is located. This shouldn't be abbreviated.	California
Country	The two-letter ISO code for the country where your organization is location.	US GB
Email address	An email address used to contact your organization.	webmaster@google.com
Public Key	The public key that will go into the certificate.	The public key is created automatically

What is a CSR's format?

Most CSRs are created in the Base-64 encoded PEM format. This format includes the "-----BEGIN CERTIFICATE REQUEST-----" and "-----END CERTIFICATE REQUEST-----" lines at the begining and end of the CSR. A PEM format CSR can be opened in a text editor and looks like the following example:

How do I generate a CSR and private key?

You need to generate a CSR and private key on the server that the certificate will be used on. You can find instructions in your server documentation or try the instructions from one of these certificate authorities:

Comodo CSR Generation Instructions
DigiCert CSR Generation Instructions
GeoTrust CSR Generation Instructions
Thawte CSR Generation Instructions
VeriSign CSR Generation Instructions

If you are familiar with OpenSSL you can use the following command to generate a CSR and private key:

openssl req -new -keyout server.key -out server.csr

How do I decode a CSR?

You can easily decode your CSR to see what is in it by using our CSR Decoder. In order to decode a CSR on your own machine using OpenSSL, use the following command:

openssl req -in server.csr -noout -text