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5.1.0-alpha2 Firmware for Original Prusa MINI  

Same Old Shane
Member Admin
5.1.0-alpha2 Firmware for Original Prusa MINI

Greetings all; 

We are pleased to announce a new Alpha build of the firmware for the Original Prusa XL, 

Please make sure to read the summary and when downloading the firmware, please make sure you select the correct version for your machine.


  • Input Shaper and Pressure Advance (XL)
  • Firmware update instructions (XL, MK4, MINI)
  • New Binary G-code (XL, MK4, MINI)
  • Cancel object directly on the printer (XL, MK4)
  • G-code streaming (XL, MK4, MINI)
  • Pre-print screen (XL Multi-Tool)
  • Wi-Fi setup with PrusaSlicer (XL, MK4, MINI)
  • Faster file transfers (XL, MK4, MINI)
  • Set ready (XL, MK4, MINI)
  • Updated bootloader (XL, MK4, MINI)
  • Bug fixes
  • Known issues

This is a public release of the 5.1.0-alpha2 firmware for the Original Prusa XL, MK4 (MK3.9) and MINI. This is an alpha 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.

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.

If you want to print on your XL with Input Shaper, you will need to flash this firmware release and install at least PrusaSlicer 2.6.1 with the XL Input Shaper profiles. In case you want to try the newest features (e.g. Binary G-code or Cancel Object), please download the PrusaSlicer 2.7.0-alpha1. If you don’t see an automatic pop-up window informing you about updated configuration files when you launch PrusaSlicer, check for updates manually. Use Configuration -> Check for Configuration Updates menu to download the new profiles. Then go to Configuration -> Configuration Wizard to add the printer with the correct profiles (please keep in mind that non-Input Shaper and Input Shaper profiles are separate and clearly named).

PrusaSlicer link

Input Shaper and Pressure Advance (XL)

This firmware release brings Input Shaper to both Single and Multi-Tool XL.

Input Shaper is a feature designed to reduce ringing (also known as echoing or ghosting) and overshoots during printing by smoothing out the accelerations and decelerations of the printer’s movements. It works by analyzing the printer’s movements and applying a filter to the input signals to reduce the ringing effect. Thanks to faster travel speed and acceleration, it can also minimize stringing. It also enables faster printing.

Pressure Advance is another important addition to the firmware’s set of features. This function aims to improve the quality of printed parts by compensating for the pressure changes in the nozzle during printing. Pressure Advance together with Input Shaper enables the printing of better-looking models, reducing ringing, overshoots, and issues with inconsistent filament extrusion. They also enable faster printing.

Precise stepping is a new implementation of stepper, that allows precise timing of motor steps. It was a necessary prerequisite for both Input shaper and Pressure advance.

We have also prepared pre-sliced Benchy G-Codes for you to test the increased speeds:

  • BonkersBenchy for Single-Tool XL takes only 12 minutes to print
  • BonkersBenchy for Multi-Tool XL (dual-head) takes 36 minutes to print

Firmware update instructions (XL, MK4, MINI)

In the case of MK4 and XL, download the firmware file below, copy it onto a USB drive, and insert it into the printer. During the boot, the printer will check for the firmware file and ask you to confirm the update.

In the case of the MINI/MINI+ printer make sure you are running either the previous 5.1.0-alpha1 or at least firmware 4.4.1, see the release notes for firmware files and instructions. Once the 4.4.1 is installed proceed to flashing the 5.1.0-alpha2 firmware. Note that the upgrade might take longer than usual.

New Binary G-code (XL, MK4, MINI)

G-code files are easy to read and interpret, but their downside is that the data is not saved efficiently and because of that the file size is often very large. Compressing the files is not the best solution because 3D printers usually run on specialized hardware and they may not have enough memory and/or CPU power to decompress such files.


Therefore, we are proposing a new standard for an open-source binary G-code format designed to encode and compress ASCII G-codes. Our testing shows that using binary G-code reduces the filesize by about 70 % on average.

To learn more about binary G-code, please visit our release notes of PrusaSlicer 2.7.0-alpha1.

QOI instead of PNG (XL, MK4, MINI)

Until this release, the thumbnails for G-code were in PNG format, which was rather resource-heavy. We have decided to switch to another format called QOI, which is way less demanding, and we can utilize the freed-up resources to bring more features in future releases.

The only downside of removing the support for PNG is that all the G-codes sliced until now, won't have a visible thumbnail on firmware 5.1.0 or newer. For now, the only solution is to reslice the G-code in PrusaSlicer 2.7.0 or newer, however, we are investigating other options.

Cancel object directly on the printer

This firmware release brings the highly-requested cancel object function. During a running print, you can open the “Tune menu -> Cancel Object” and select an object that you wish to stop printing (but you can also resume it, in case you select an incorrect one). The print will continue running and any G-code commands related to the canceled object will be ignored. This is perfect for cases where you’re printing many objects at once and one of them gets loose on the build plate.

The easiest way to stop printing an object is to use the “Cancel Current” function - simply wait for the nozzle to reach the object you want to cancel and then select this option.

G-code streaming (XL, MK4, MINI)

This feature was designed to enable instant network printing. With G-code streaming support, you can start the print without the need to download the entire file to the printer beforehand. Instead, only a small portion of the file is downloaded, allowing the print job to start almost immediately. The remaining G-code is automatically downloaded while the print is in progress. In most cases, the print starts within seconds.


As you can see from the graph above, the largest G-code (the V6 engine) originally took about 36 minutes to download before the printer could start printing. With the new G-Code streaming option, the print starts in 25 seconds.

The system is ready for unexpected scenarios, e.g., if there is a temporary problem with the network or there is a short power outage, the printing and streaming will resume automatically. Only in case of a longer network interruption, the printer will wait for the user to confirm to resume the print. In case of a major network outage when the connection cannot be re-established, please copy the G-code onto the USB drive manually.

This feature is currently available for both Connect and PrusaSlicer 2.7.0 or newer.

Pre-print screen (XL Multi-Tool)

When you slice a multi-material object, the resulting G-code carries information about how individual materials/extruders are assigned to various parts of the object. This new screen allows you to remap the extruders/materials to different slots. For example, you can switch extruders one and three if you find out that the loaded colors do not match the layout in the G-code.

Wi-Fi setup with PrusaSlicer (XL, MK4, MINI)

Setting the Wi-Fi on your printer requires creating a config file with Wi-Fi credentials (SSID and password). Until now, this file was generated by the printer during the network setup and the user was supposed to edit this file in the computer and then return back to the printer.

PrusaSlicer 2.7.0 or newer allows you to create the same config file in advance. In PrusaSlicer go to Configuration -> Wi-Fi Configuration File. Select a wireless network, fill in your Wi-Fi password, and choose the USB drive where you want to upload the file.

After you insert the USB drive into the printer, the system will recognize the config file and offer you to start the network setup. Once the Wi-Fi connection is established, the printer will ask you, if you want to delete the config file. Deleting the file is recommended as it includes the Wi-Fi password.

Faster file transfers (XL, MK4, MINI)

For those, who prefer using a USB flash drive or copying the entire file at once, this release brings several optimizations, which should result in faster transfer speeds. However, we highly recommend trying the G-code streaming option first.

Set ready

Another highly-requested feature was to have the ability to set the printer into a ready state for a scheduled remote print. This is especially useful for, e.g., large print farms, where you can prepare multiple printers at once and then start printing remotely from your office.

To set the printer into the ready state, go to “Control -> Set ready”. You can do the same in Prusa Connect. More improvements to this feature will be introduced in future releases.

Updated bootloader (XL, MK4, MINI)

While flashing this firmware release, the bootloader will be updated as well. The new bootloader improves support for OTA (over-the-air) updates from Prusa Connect. Also, the graphics of the bootloader now matches the rest of the UI.

Bug fixes

  • Manual z-axis movement (using the long press shortcut) is now smooth and without stuttering. (MK4)

Known issues

  • While connecting to the Wi-Fi or using the feature “Cancel Object” the printer can in some scenarios crash (BSOD screen). Please save the dump file and open an issue on GitHub.
  • USB flash drive disconnect can occur. Try reinserting the drive to continue using it. In the case of G-code streaming, the system might not be able to resume printing. Should that happen, please copy the file on the USB drive instead.
  • The remaining time and print progress are sometimes not accurate, the developers are aware of this and the fix will be provided soon.
  • Multi-Tool XL 3D printers can get stuck while checking heaters during the self-test, please restart the printer.
  • Another print will get started over the previous one, this is a very rare issue. For now, the only solution is to start the print again.
  • Printer status in Prusa Connect can flicker between online and offline.
  • Octoprint is not working as expected (e.g. the filament runout or print fan checks are missing). We have some fixes already in the pipeline.
  • MINI sometimes deletes the file with Wi-Fi credentials without user confirmation.
  • Wi-Fi credentials dialogue is in some scenarios displayed over other screens (e.g. filament sensor calibration)
  • The footer setting can get deleted during the firmware update.

              Download link;

              How to flash the firmware;

              Please report any bug here:

Shane (AKA FromPrusa)

Posted : 23/10/2023 7:31 am
Famed Member
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

After seeing a lot of issues reported with Alpha-1 I was reluctant to load *any* of the alphas but eventually I caved 🙂 Happy to report that it works *great* on my Minis. Even though they have Dragon hotends, any prints I've done so far with IS look spectacular. I'm also very happy with the upload speed (at least over Ethernet, I haven't tried wifi) but most importantly, finally support for PrusaConnect!!! This brings all my printers now into one common management system. The only problem I've seen is inconsistency in the display of preview images in PrusaConnect, sometimes they show, next time, same file sliced again, they don't.

Posted : 28/10/2023 4:06 pm
Eminent Member
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

I have upgraded and so far little issues.
I haven't tested if teh X-axis homing works without foamtape but so far results are OK.


However I do find my products to have size issues:

- bottom 1-4 layers are wider than the rest.
- overal size is smaller than desired (50mm becomes 49,8mm)

Posted : 29/10/2023 8:00 pm
Active Member
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI and Prusa Connect

I just tried sending g-code to the Mini+ and got a 'heap' error and a BSOD with lots of data on it? Is this a general error that will be fixed in subsequent release?

Posted : 29/10/2023 9:19 pm
Estimable Member
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

wifi upload on alpha2 is much faster than it was on alpha1...

Posted : 30/10/2023 8:17 pm
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

Ich hatte und habe kaum Probleme mit der alpha-Firmware für meinen MINI+. Die alpha-1 Firmware ließ sich Problemlos installieren, und alle Funktionen liefen auf anhieb, auch WLan.

Bei der alpha-2 Firmware war es das gleiche.

Ich hatte bei beiden Versionen einige BSOD's, diese wurden auch von der Firmware bemerkt und ein Dump auf den USB-Stick geschrieben.

Leider gab es dann unter der alpha-2 ein massives Problem beim versuch mit generischem PETG zu drucken, was zur Zerstörung der PEI-Schicht meines Druckbettes führte, trotz First-Layer-Kalibrierung vorher wurde die Nozzle zu tief herunter gefahren und schrammte über das Druckbett. Beim Versuch, die PETG Filamentreste vom Druckbett zu entfernen, löste sich die PEI-Schicht mit ab.


Posted : 08/11/2023 12:16 pm
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

I have motived the same.  That is about the only thing I have noticed. 

Posted by: @mixer3d

wifi upload on alpha2 is much faster than it was on alpha1...


Chuck H
3D Printer Review Blog

Posted : 20/11/2023 11:45 am
Estimable Member
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

There is a new FW available  5.1.0-beta and the slicer in PrusaSlicer 2.7.0-rc1 version, i'm using both since few days without any issues.

Posted : 20/11/2023 1:50 pm
RE: 5.1.0-alpha2 Firmware for Original Prusa MINI

An meinem Prusa Mini+ hat die 5.1.0-Beta mit PrusaSlicer 2.7.0-rc1 den Fehler "Thermal Runway" bei PET und  bei der Temperatur über 220 Grad, verursacht. Error.

Habe danach die 5.1.0-alpha2 und den PrusaSlicer 2.7.0-alpha 1 und Werksreset gemacht.Fehler war weg.

Beta Version wieder installiert und Werksreset gemacht - Fehler wieder da.

Bleibe also bei der Alpha- Version. 

Posted : 21/11/2023 9:10 pm