CrystalDiskMark Troubleshooting

Benchmark test failed or cannot create test file

Cause: Not enough privileges to create the test file on the drive.

Solution:

• Run CrystalDiskMark as Administrator (right-click executable, Run as administrator).
• Ensure the drive has enough free space (at least the test size, e.g. 1 GiB).
• Temporarily disable antivirus real-time scan on that drive and retry.

Network drive not showing

When run as Administrator, Windows does not show mapped network drives.

Solution: Run CrystalDiskMark without Administrator rights. When UAC appears, click No. Start as normal user so the network drive appears.

See FAQ

Results lower than expected or than other software

Possible causes: different test data (Random vs 0 Fill), test size, background disk usage, or controller/port (e.g. NVMe in x2 slot).

Use same tool and settings when comparing. For NVMe try Settings then NVMe SSD profile. Ensure drive is not thermal throttling.

Program won't start or crashes

• Install latest Visual C++ Redistributable for your architecture.
• Try the ZIP version from a short path (e.g. C:\CDM).
• Check supported OS (Windows 7+). Allow CrystalDiskMark in antivirus.

Save as image or copy does not work

Run as Administrator once. On Windows 11 check clipboard privacy settings. Alternatively use File then Save (text).

Test very slow on USB or external drive

Use a smaller test size (e.g. 64 MiB or 128 MiB). For USB 3.x ensure port and cable support USB 3.

Drive not listed or greyed out

Ensure the drive has a letter assigned in Disk Management and has enough free space (at least the test size). BitLocker or other encryption can sometimes affect visibility. Try running as Administrator if the drive is a system or protected volume.

Results much lower after a while (thermal throttling)

NVMe SSDs and some SATA SSDs reduce speed when they get hot. Let the drive cool down, improve case airflow, or add a heatsink. Run the benchmark again after a few minutes of idle. CrystalDiskInfo can show drive temperature if you want to monitor it.

Antivirus or security software blocking the test

Some security products block programs that write large amounts of data. Add CrystalDiskMark to the exclusion or allow list, or temporarily disable real-time scanning for the test folder/drive and run the benchmark again.

Windows says the drive is in use

Close programs that might be using the drive (file manager, backup, sync tools, media players). Do not run the benchmark on the same drive where the OS is running heavy swap or temp activity. If needed, run from another drive or reboot and try again with minimal software running.

NVMe drive much slower than expected (e.g. only 1,700 MB/s on PCIe 4.0)

Check that the NVMe is in a slot that supports the correct link width (e.g. x4). Some motherboards have M.2 slots that run at x2. Also ensure you are using the NVMe SSD profile in CrystalDiskMark (Settings or profile menu). Update the NVMe driver (e.g. from the motherboard or SSD vendor). Thermal throttling after repeated runs can also cut speed; let the drive cool and test again.

Program shows wrong or very old Windows version

CrystalDiskMark reads the OS version for compatibility. If it displays an incorrect or outdated Windows version, update Windows to the latest build and ensure you have the latest CrystalDiskMark version. On some virtual machines or custom setups the reported OS can differ; the benchmark usually still runs. If you see errors, try the portable (ZIP) build.