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5.1.0-beta Firmware for Original Prusa MK4  

Same Old Shane
Member Admin
5.1.0-beta Firmware for Original Prusa MK4

We are happy to announce that our latest firmware has entered into Beta release status. Please make sure to read all the information and download the correct version of the firmware for your machine.


  • Unified self-test (XL/MK4/MK3.9)
  • Alpha support of Octoprint
  • Changes & Improvements
  • Bug fixes

This is a public release of the 5.1.0-beta firmware for the Original Prusa XL, MK4 (MK3.9) and MINI. This is a beta release intended for experienced users. The features in this firmware are still under development and may not perform as expected. Should you encounter any bugs or issues with the printer’s performance, please report them via GitHub or in our forums.

This firmware incorporates new features (Binary G-code, Cancel object, G-code streaming, Input Shaper for XL) that were initially introduced in the previous releases 5.1.0-alpha1 and 5.1.0-alpha2.

Please note that this is a testing firmware developed primarily on stock unmodified printers. In case you are running any 3rd party upgrade, exercise caution and let us know in case of any issues.

Unified self-test (XL/MK4/MK3.9)

With this firmware release, we've standardized the self-test procedure for XL, MK4, and MK3.9 printers. While the steps remain largely unchanged, there are updates to the UI. If your printer is already calibrated, your results will be seamlessly transferred.

The firmware also no longer creates log files on the USB drive when running the Selftest.

Alpha support of Octoprint

This release includes improvements for users utilizing OctoPrint for remote printing. It's important to note that this implementation is still a work in progress, some features will be added (fixed) in future releases.

Current OctoPrint limitations

  • Pause/Resume commands from OctoPrint are not functional (Pause/Resume the print using the screen for now).
  • The Stop print command from OctoPrint is not operational (Stop the print using the screen for now).
  • Multitool XL - If the tool crashes, the print cannot be recovered.

Changes & Improvements

New unified dialogue for unfinished self-test

The MK4/MK3.9 now displays a redesigned screen that notifies users when not all self-test steps are completed. This screen also replaces another UI dialog informing about a disabled filament sensor if the user has chosen to skip sensor calibration.

Updated Wi-Fi credentials system

Now, the system offers to update Wi-Fi credentials from a file on the USB drive only if the credentials are in the expected format.

Prusa Connect and PrusaLink improvements

This firmware brings better file synchronization handling and improved retry conditions. G-code downloads have been optimized for better server performance. Cleanup and recovery of Connect transfers have been also improved. PrusaLink has been updated - the download button is disabled when the file is still being downloaded from Connect.

Another improvement brings better transfer progress reporting and communication between the printer and Connect.

Smaller UI tweaks

  • The Filament button has replaced the “Change” button in the pre-print screen
  • Purge Filament option is always available, independent of the current filament sensor state


  • Network transfer is now recovered when USB is unplugged and plugged back in during file transfer
  • Fixes for printer freezing when the USB stops responding
  • “USB file error” when streaming a G-code has been fixed
  • The printer used to show a BSOD screen instead of a red screen when a thermal issue was detected, this is now fixed
  • A rare bug that could cause an issue with selecting prints in the file browser (item selection was not available) has been fixed
  • A rare condition of a reentrant crash recovery has been fixed
  • MINI only: fixes for common homing issues
  • XL and MINI: fixed migration of footer settings
  • XL only: The Reprint option has been fixed - once you reprint a finished project, you will correctly see the filament mapping screen before the print starts
  • Occasional artifacts in the side scrollbar have been fixed
  • When scanning for G-code metadata, the printer could encounter a memory corruption bug. This is now fixed.
  • The printer could freeze while waiting for Loadcell samples (G-code G28/29 or in Tool Offset Calibration). This is now fixed.
  • The cause of the “configASSERT” BSOD has been fixed
  • Occasional unavailability of some items in the Footer Settings (e.g., not able to pick the “Sheets” footer item on the MINI) has been fixed
  • XL only: heater test in Selftest has been fixed
  • The cause of the stack overflow BSOD in media prefetch tasks has been fixed
  • The bug causing the printer to get stuck at the Downloading screen has been fixed
  • The Input Shaper menu now properly shows the current values
  • Fixes related to USB drive and file access
  • MK4 only: a bug that could prevent the Wi-Fi from working correctly has been fixed
  • Issues with Tool Crash Recovery (within M600 and pauses) have been fixed
  • The “Negative step time” BSOD has been fixed
  • A rare case of a blob being created at the seam location has been fixed
  • Improved the robustness of the internal random number generator, improves Connect safety features
  • Issues with the USB CDC (serial port) connection to PC have been fixed

              Download link;

              How to flash the firmware;

              Please report any bug here:

Shane (AKA FromPrusa)

Posted : 23/11/2023 8:56 am
Estimable Member
RE: 5.1.0-beta Firmware for Original Prusa MK4

I found and loaded it.  It is not listed as Beta on the web page.  It lists as final release.   Also the 2.7.0 slicer is release code now.  

Posted : 24/11/2023 7:00 pm
Midnight rambler
RE: 5.1.0-beta Firmware for Original Prusa MK4

First layer fails every time now....might have to try and revert FW.

Posted : 24/11/2023 7:17 pm
Active Member
RE: 5.1.0-beta Firmware for Original Prusa MK4

If youre using pla with input shaper make sure to get those temps up higher. I struggled with terrible first layers until i went back to default generic pla which is 230 first layer and 220 other. I still need to tweak it to improve bridging but there is nothing worse than 1st layer problems, ruins the fun

Posted : 25/11/2023 8:09 am
Eminent Member
RE: 5.1.0-beta Firmware for Original Prusa MK4

I have the same problem, the first layer always fails.

I have gone back to the previous version.

Posted : 25/11/2023 11:31 am
Noble Member
RE: 5.1.0-beta Firmware for Original Prusa MK4

Thx for this all new improvements SOS , but when could we have more option and really good useful tools on the prusalink !! i mean just the same with my mk3 and the RPIOW !! now with the mk4 i can't see cam can't control can't sort out by date !! which is really important and so useful when u load same gcode but with minor stl change you must look at the time or date !!!  in the whole file list !!!

i read that prusalink is not on the top pile of the task list !! is it so complicate and different from mk3 + rpio than MK4 and the xbuddy 32bits !!

Posted : 25/11/2023 12:01 pm