Grbl

Grbl is open-source firmware that turns an Arduino with an ATmega328P chip into a CNC motion controller for milling machines, running g-code.

Made by Gnea Research LLC.

Licenses

Code: GPL-3.0-only (opens in a new tab)
Read by Robotheca from COPYING (opens in a new tab) (GPL-3.0-only) at commit bfb67f0 (opens in a new tab), on 16 Oct 2026.
Commercial use: Yes

Copyleft: Modified source must be published.

Written in optimized C for AVR chips, it produces stable control pulses up to 30kHz.
Accepts standards-compliant g-code, including arcs, circles and helical motion; tested with several CAM tools.
Plans acceleration with a look-ahead of up to 16 motions for smooth cornering.
Supports real-time overrides for feed, rapid, spindle speed and coolant, plus a separate jogging mode.
Offers a laser mode with dynamic power scaling by speed, and a sleep mode that disables everything until reset.
Reports errors and alarms with codes and uses message prefixes to simplify GUI parsing.

Written by Robotheca from the project's README (opens in a new tab) at commit bfb67f0.

Difficulty: Beginner
Hardware it needs, as the project states it: Runs on an Arduino with a 328p processor, such as the Uno, Duemilanove, Nano or Micro; Arduino Mega2560 support has moved to the separate Grbl-Mega project.
How to start: The project's website (opens in a new tab)

Checked on GitHub on 16 Oct 2026.

No robot on Robotheca is linked to it yet. Links come from a robot's robot.yaml, from its dependency files read as text, or from Robotheca's editors.

Robotheca lists software as a reference: nothing is hosted or run here, and every fact links to where it was read.