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Create a Dummy Test File of Any Size with fsutil

Instantly generate a multi-gigabyte empty file to test copy speeds, storage, or network transfers.

WindowsFilescmddummy-filesLow risk
Run `fsutil file createnew D:\Test\testfile.bin 1073741824` to create a 1 GB test file in seconds.

01Command

Command
$ fsutil file createnew D:\Test\testfile.bin 1073741824

02What it does

fsutil file createnew allocates a file of the exact byte length you specify (1073741824 bytes = 1 GB) without writing data, so even a huge file appears instantly. It's handy for testing folder transfers, USB write speeds, or how applications behave with large files. The file is created in seconds because the contents are not actually written.

03Risk

RiskLow risk
RequirementsBuilt into Windows; the byte size is required (e.g. 1073741824 = 1 GB).
!Warning: The created file contains no meaningful data — it's for size and speed tests, not content.

04Undo

Undo
$ del D:\Test\testfile.bin

05Sources

  • FSUtil — File system utilities
    SS64 · technical · 2026-09-17
    Evidence: Includes the FILE CREATENEW command that creates a new file of a given size.
  • fsutil file
    Microsoft Learn · vendor-doc · 2026-09-17
    Evidence: Documents "fsutil file createnew <filename> <length>" which creates a file of the specified name and size.

Last verified: 2026-09-19 · Category: Files & Folders

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