What Is a CSR File?

This file is used as a signing request for a digital certificate

By
Tim Fisher
Photo of Tim Fisher, Lifewire GM and Writer
Tim Fisher
Senior Vice President & Group General Manager, Tech & Sustainability
  • Emporia State University

Tim Fisher has more than 30 years' of professional technology experience. He's been writing about tech for more than two decades and serves as the SVP and General Manager of Lifewire.

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Updated on December 11, 2022

What to Know

  • A CSR file is a certificate signing request file.
  • Open one with OpenSSL or Microsoft IIS.
  • Convert to PEM, PFX, P7B, or DE with an online CSR converter.

This article describes what a CSR file is, how to open one, and what your options are for converting one to a different certificate format.

What Is a CSR File?

A file with the CSR file extension is a certificate signing request file used by websites to authenticate their identity to a Certificate Authority.

These files are partially encrypted, with the encrypted portion describing the domain, email address, and country/state of the applicant. Also included in the 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 file.

CSR files in Windows 10

CSR is also an abbreviation for some other technical terms, but none of them have anything to do with the 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

Some CSR files can be opened with OpenSSL or Microsoft IIS.

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

How to Convert a CSR File

Most file formats can be converted to other formats with a free file converter. This format is a bit different, so there aren't 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 here.

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 file there and then choose an output format to save it to.

  1. Go to SSLShopper.com, and select Choose File.

    The SSL Shopper website.

  2. Select the file to convert, and press Open.

    Browsing for a CSR file.

  3. Under Type of Current Certificate, select the type.

    Selecting the current certificate type.

  4. Under Type to Convert To, select the type you wish to convert the file to.

    Selecting conversion type.

  5. Select Convert Certificate.

Still Can't Open It?

One reason you can't open the file might be that you're misreading the extension and confusing another format for the certificate signing request format. There are lots of file extensions that look like they read ".CSR" when they're really just similar looking.

Some examples can be seen with CRS, CSH, CSV, CSS, and CSI files. Although they look 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 to research which software programs can open or convert your file.

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