Snapmaker Open-Sources Its U1 Klipper Code With a Day to Spare
Snapmaker has released the modified source code for the three open-source projects that underpin the Snapmaker U1's firmware: Klipper, Moonraker, and Fluidd. The repositories went live on GitHub on March 30 – the final day before a deadline the company set for itself.
The U1, a four-toolhead CoreXY machine that raised over $20 million on Kickstarter, runs a customized version of Klipper. It also uses the Fluidd web interface and Moonraker API. All three projects are licensed GPLv3, which requires anyone distributing modified versions should make the corresponding source code available.
Snapmaker had been shipping U1 units to backers since late 2025 without publishing that source, prompting questions about compliance – the sticking point being the three-and-a-half month gap between distributing the firmware, and making it available to the user.
In a January 2026 forum thread, community members began to dissect the firmware and, comparing it to upstream Klipper, noted the scope of the modifications. Snapmaker’s Kickstarter FAQ initially promised the source would arrive “before March 2026.” A wiki update on March 6 quietly corrected this to “before the end of March 2026,” which the company attributed to an error in wording.
The manner in which Snapmaker has released the code is of note. A blog post about the release details not just what they’ve changed but roughly by how much: approximately 20 percent of the codebase is custom, the company says, including a redesigned tool-switching workflow for parallel multi-toolhead operation, custom eddy-current bed leveling, multi-toolhead XYZ offset calibration, power-loss recovery, filament tangle detection, and RFID-based filament recognition. Moonraker saw around 15 percent of its codebase modified, primarily for Snapmaker Cloud integration, 3MF file handling, and local network management. The company says its changes to Fluidd were minor.
Why does any of this matter? Well, license obligations notwithstanding, for U1 owners, having access to the source means the ability to inspect, modify, or even build their own firmware. For the independent firmware developers who’ve already been doing this from reverse-engineered code, it means working from a proper foundation rather than a moving target.
This kind of transparency about the nature and extent of modifications is unusual in the space. The industry’s track record on Klipper GPL compliance is, to put it generously, patchy. Creality notably faced community pressure over the K1 in 2023 and the K2 Plus in 2025, while Elegoo’s Centauri Carbon launch later was subject to a successful community pressure campaign for compliance. In most of these cases the source code – when it eventually appeared – arrived with little or no context about what had been changed.
Bucking this trend, Snapmaker’s post about the release reads more like a changelog than a compliance filing.
There are boundaries, though. The blog post states that “certain advanced capabilities within the U1 system are implemented through independently developed modules” not derived from Klipper, Moonraker, or Fluidd. These include intelligent flow rate auto-calibration and AI-based defect detection. Separately, Snapmaker’s wiki confirms the RFID filament recognition system is proprietary, with no plans to open-source it.
By the time Snapmaker published its repositories, independent firmware like paxx12’s SnapmakerU1-Extended-Firmware has appeared offering features not present in the original, including root SSH access, full Fluidd and Mainsail frontends, hardware-accelerated WebRTC camera streaming, external RFID reader support, and OctoEverywhere integration for remote access and AI failure detection.
Snapmaker’s own involvement in merging requests and picking up community-developed fixes and features will be evidence of this being a successful release, rather than a simple compliance dump. You can check it out for yourself over on GitHub.
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License: The text of "Snapmaker Open-Sources Its U1 Klipper Code With a Day to Spare" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.