Open firmware is printer software whose source code is published under a license that lets anyone read, modify and redistribute it. Marlin, Klipper and Prusa Firmware Buddy all use the GNU General Public License (GPL) version 3. Closed (proprietary) firmware stays under the manufacturer’s control, including what can be changed and which outside tools can talk to the printer. Both kinds print well. The difference is who controls the software.
What does 3D printer firmware do?
Firmware is the software running on a printer’s control board. It reads the G-code (machine instructions) a slicer produces and turns it into motor movements, heater control, fan speeds and sensor checks. It also enforces speed and acceleration limits and runs features like input shaping (vibration cancellation) and pressure advance (extrusion compensation for speed changes).
The slicer decides what to print; the firmware decides how the hardware moves. Firmware sits between your files and the printer, so its openness decides what you can adjust and which slicers and control interfaces can connect. It also decides whether the printer depends on the manufacturer’s servers.
What is Marlin firmware?
Marlin is an open-source firmware that runs directly on the printer’s microcontroller. Its documentation describes it as “an open source firmware for the RepRap family” of 3D printers, “licensed under the GPLv3 and is free for all applications.” Settings are chosen at compile time, so changing features usually means rebuilding the firmware and flashing (installing) it on the board.
The Marlin project says it runs “on a huge number of inexpensive micro-controllers,” from 8-bit AVR boards to 32-bit ARM boards. The same page says it became “a standalone open source project on August 12, 2011.” Its documentation lists Prusa, Creality and Ultimaker among commercial users.
What is Klipper firmware?
Klipper is an open-source firmware that splits the work between a general-purpose computer and the printer’s microcontroller. The computer (often a Raspberry Pi) calculates movements, and the microcontroller times each step precisely. Configuration lives in a text file, so most changes need no recompiling. Klipper is released under GPL-3.0.
The Klipper documentation says it uses “an application processor (such as a low-cost Raspberry Pi)” to calculate printer movements and that “all of Klipper’s configuration is stored in a standard config file which can be easily edited.” It supports Cartesian, delta, CoreXY and several other kinematics (motion layouts; see the motion systems guide). It also supports input shaping and “smooth pressure advance.” Web interfaces such as Mainsail and Fluidd are common front ends.
What is Prusa Firmware Buddy?
Prusa Firmware Buddy is the open-source firmware Prusa Research uses on its 32-bit printers. Its GitHub repository lists support for the Original Prusa MINI/MINI+, MK3.5, MK3.9, MK4, Original Prusa XL and Prusa CORE One. The source code is licensed under GNU GPL v3, and the project credits Marlin as its core driver.
For owners, Prusa’s product pages connect the open code to offline use. Prusa Research states for the Original Prusa MK4S: “Our code is open source, so you can always check that we aren’t cheating or stealing your files,” and that the printer “can be configured completely without internet access.” For the Prusa CORE One, the product page (which now presents its CORE One+ successor) says the firmware source code “is on GitHub.”
What does closed firmware mean on printers like Bambu Lab?
Closed firmware means the manufacturer does not publish the source code and controls which features and connections the printer allows. Bambu Lab printers use proprietary firmware. Owners get the features the company ships, including local area network (LAN) modes. They cannot inspect or rebuild the firmware, and third-party tools connect only through the interfaces the company provides.
In January 2024, 3D Printing Industry quoted Bambu Lab describing its approach as “the Apple way.” The outlet reported that an optional path to third-party firmware on the X1 was a “one way ticket” that revokes the warranty and support.
In January 2025, Bambu Lab’s blog announced an authorization mechanism for printer control. The same post states that “LAN mode through Bambu Connect will require neither internet access nor a user account.” It also describes a Developer Mode for the X1, P1, A1 and A1 Mini that leaves “the MQTT channel, live stream, and FTP open” and “must be manually enabled on the printer.” MQTT is a messaging protocol and FTP (File Transfer Protocol) moves files.
The slicer side is partly open. Bambu Lab’s GitHub repository says Bambu Studio “is based on PrusaSlicer” and is licensed under AGPL-3.0 (the GNU Affero General Public License), while “the bambu networking plugin is based on non-free libraries.”
What does “open” change for owners?
Open firmware changes four things: you can read and modify the code, third-party slicers and host software can connect without manufacturer permission, the printer does not need a vendor cloud account, and community support can continue if the manufacturer stops updating a model. Closed firmware can still offer local modes, but on the manufacturer’s terms.
|
Open firmware (Marlin, Klipper, Prusa Firmware Buddy) |
Proprietary firmware |
| Source code |
Published under GPL-3.0 |
Not published |
| Modifying behavior |
Possible, by editing config or code |
Limited to settings the maker exposes |
| Third-party slicers and hosts |
Can connect through standard G-code and host software |
Through interfaces the maker provides |
| Cloud dependence |
Not required by the firmware itself |
Varies; check for a local or LAN-only mode |
| After the maker stops updates |
Community can continue development |
Depends on the maker |
Proprietary systems often tie the slicer, printer and app closely together. Open systems may need more configuration. The trade is control and longevity against a managed, integrated setup.
Which 3D printers support Klipper out of the box?
Printers that ship with Klipper or a Klipper-based firmware include the Elegoo Neptune 4, which Elegoo says “comes pre-installed with Klipper firmware.” Voron kits run it too: their documentation says “all stock Voron printers run on the Klipper firmware.” Creality publishes a Klipper-based firmware for its K1 series on GitHub.
Some details to check:
- Stock Klipper vs a fork. Creality’s K1_Series_Klipper repository describes itself as a clone of the upstream Klipper project with “updated relevant functions,” released under GPL-3.0. On its Creality K1 Max product page, Creality refers to the system as “Creality OS” rather than Klipper.
- Access. Some Klipper-based printers expose the full configuration and a standard web interface. Others lock it until you opt in. Creality’s K1 firmware release notes say SSH login to the root account works only after you accept a root warning under Settings > Root Account Information.
- Updates. A vendor fork may lag the upstream project.
The printer database records each printer’s firmware name and whether its source is open, on the same spec sheet for every model.
What should you check about firmware before buying?
Check four things on the spec sheet and the maker’s documentation: the firmware name and license, whether the printer works fully offline or on a local network, which slicers and host tools it supports, and how long the maker commits to updates. The firmware name alone does not show how much of a vendor’s build stays open.
If you plan to modify your printer or run it with third-party tools, an open-source firmware keeps those options available. If you prefer a managed setup, check that the proprietary system documents a LAN mode. For how firmware fits alongside other specs, see the guide to comparing printers.
