What Is a CSR File?

How to open, edit, & convert CSR files

Screenshot of several CSR files in Windows 10
CSR Files.

Tim Fisher

A file with the CSR file extension is a Certificate Signing Request file used by websites to authenticate their identity to a Certificate Authority.

CSR files are partially encrypted, with the encrypted portion describing the domain, email address, and country and state of the applicant. 

Also included in a CSR file is the public key. The CSR file is created using the public key and the private key, the latter of which is for signing the CSR file.

CSR is also an abbreviation for some other technology terms, but none of them have anything to do with the CSR file format described on this page. Some examples include cell switch router, customer self repair, content service request, and control and status register.

How to Open a CSR File

CSR files can sometimes be opened with software such as OpenSSL or Microsoft IIS.

You could also open a CSR file with a text editor but it probably wouldn't be very useful. Since the primary information in a CSR file is encrypted, a text editor would serve to only show garbled text when viewed as a text file.

If you find that an application on your PC does try to open the CSR file but it's the wrong application or if you would rather have another installed program open CSR files, you can change the default program for a specific file extension in Windows.

How to Convert a CSR File

Most file formats can be converted into other formats with a free file converter, but CSR files are a bit different and so there aren't very many dedicated CSR converters available. For example, a PNG file is popular enough that lots of free image file converters can save it to a different format, but that's not really the case with CSR files.

The easiest way to convert CSR to PEM, PFX, P7B, or DER certificate files is with the free online SSL Converter at SSLShopper.com. Upload your CSR file there and then choose an output format to save it to.

If you're wanting to convert the CSR file to CRT (Security Certificate). It involves using some commands with OpenSSL.

Still Can't Open Your File?

One reason for why you can't open your file might be that you're misreading the file extension and confusing another format for the Certificate Signing Request format. There are lots of file extension that look like they read ".CSR" when they, in fact, are just very similar looking.

Some examples can be seen with CSH and CSI files. Although they might like they have something in common with CSR files, beyond their file extension letters, they're actually totally different kinds of files that are opened with different programs.

Double-check the file extension your file is using and then use that as research for help finding out which software programs can open or convert the file.