USB Drive Not Reading
Prusa 3D Printer
Severity: MinorWhat Does This Error Mean?
If the Prusa printer does not show files from the USB flash drive, the drive may be in the wrong format, too large, or have long filenames. Format as FAT32 and use short filenames.
Affected Models
- Prusa MK4
- Prusa Mini+
- Prusa XL
Common Causes
- USB drive formatted as NTFS or exFAT instead of FAT32
- Drive capacity too large (some printers limit to 16-32GB)
- Filenames too long or containing special characters
- USB drive not fully inserted
- Drive is faulty
How to Fix It
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Format the USB drive as FAT32.
Right-click in Windows > Format > FAT32. For drives over 32GB, use a tool like Rufus or guiformat.
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Use a small USB drive (8-16GB).
Very large drives (64GB+) can sometimes cause issues. 8-16GB drives are ideal.
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Keep filenames short with no special characters.
Use only letters, numbers, underscores, and dashes. Keep names under 30 characters.
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Try a different USB drive.
Some USB drives have compatibility issues. The drive included with the printer is known to work.
Frequently Asked Questions
Can I print directly from PrusaSlicer via USB cable?
On the MK3S+ yes, but it is not recommended for long prints — if the computer sleeps, the print fails. The MK4 and Mini use USB flash drives, not USB cable printing.
Does the MK4 support network printing?
Yes. The MK4 supports PrusaLink for network printing over WiFi or Ethernet. You can send files directly from PrusaSlicer without using a USB drive.