Create a specific size file for testing

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Goal / Scope

The goal of this document is to provide a method for quickly creating a file with a specific size.


There are times when a file of a specific size may be required to test functionality of a specific solution.  An example of this would be testing file attachment size limitations when sending email.  Many email services and solutions have limits on the maximum size of a file that can be sent via the mail server.  In order to set and or test this, a file of similar size is necessary for a sending a test message to verify the maximum message size has been set correctly and can successfully deliver the message to the recipient.

Methodology / Process Steps

In order to create a file of a specific size in Windows, a utility called fsutil.exe has been included with more recent versions of Windows.  This utility allows “dummy” file creation and allows many different parameters including file size.  The following is an example of the syntax required to create a file called testfile.txt with the size of 20MB.

fsutil.exe file createnew c:\testfile.txt 20000000

For a full list of options and parameters, please visit

Known Issues / Troubleshooting

This section is for the issues that have well defined and tested solutions.

(currently there are no known problems or issues with this utility.)

Problem: |

Solution: |


Technet Article Reference for fsutil.exe file:

Technet Article Reference for fsutil.exe: (complete list of options)

Last Updated On October 24, 2017