Prusa’s xBuddy-based printers update from a .bbf file on a USB drive, even when the update is started from Prusa Connect.
1. Read the release notes
Prusa publishes firmware releases on GitHub: Prusa-Firmware-Buddy releases. Check for required steps such as calibrations and for known issues. Also see our tracked verdicts.
2. Download the firmware for your exact model
Get the package from your printer’s product page (MK4 and MK4S, or MK3.9 and MK3.9S, are different firmware). Follow Prusa’s How to update firmware guide:
- Make sure the USB drive has no other
.bbffiles on it. - Copy the new
.bbfto the root of the drive (not in a folder). A FAT32-formatted drive is the safe choice. - Insert the drive and press the reset button. The bootloader offers to flash if the file is newer.
- Select FLASH and confirm.
3. OTA through Prusa Connect still needs USB
Prusa Connect can transfer the update for you, but a USB drive must still be inserted in the printer.
4. “Different FW Required” errors
If the printer detects firmware for a different model (e.g. after an upgrade kit), it shows an error such as #13701 or #26701. Prusa’s Firmware Update Required article explains the fix: flash the firmware that matches your actual printer model.
5. After updating
Run any calibrations the release notes call for, then print a small test part before a long job.
Checklist
- Release notes read
- Correct model’s
.bbf, alone, in the USB root - Reset → FLASH
- Post-update calibrations + test print