Klipper is an alternative firmware for 3D printers' micro-controllers. The default firmware for most 3D printers is Marlin. Klipper consists of 2 parts, the micro-controller firmware to control basic motor and print head and software running on an attached general purpose computer like a Raspberry Pi or a PC.

Details on https://www.klipper3d.org

Arksine/Moonraker is a Python 3 based web server that exposes APIs which client applications can use to interact with Klipper.

There are several Web interfaces that can interact with Klipper through Moonraker's APIs:
Octoprint
Mainsail by Mainsail-Crew





Fluidd by Cadriel

Touchscreen GUI:
KlipperScreen by jordanruthe