QMK Firmware for Custom Keyboards

QMK (Quantum Mechanical Keyboard) is an open-source firmware for custom mechanical keyboards, enabling users to fully customize key mappings, lighting effects, macros, and other behaviors on supported keyboard controllers. Originally forked from TMK Keyboard Firmware (by Hasu) in 2014, QMK was developed by Jack Humbert (founder of OLKB/Ortholinear Keyboard) and has grown into the most widely used firmware in the custom mechanical keyboard community. Key features: support for over 2,500 keyboard layouts and PCBs contributed by the community, covering everything from single-key macro pads to full-size ergonomic split keyboards. Keymap customization allowing every key to be remapped, including layers (up to 32), tap-dance (different actions based on tap count), hold-tap (modifier on hold, key on tap), and combos (multiple keys pressed simultaneously triggering an action). RGB lighting support including RGB Matrix and RGB Light with dozens of animation modes (breathing, rainbow, snake, knight rider) and HSV color control. Macro support for recording and replaying keystrokes, Unicode input, and custom C functions. VIA and Vial support for real-time, on-the-fly key remapping through a graphical interface without reflashing. VIA is a web-based and desktop app providing a visual keymap editor. MCU support for AVR (ATmega32U4, ATmega328P), ARM (STM32F103, STM32F303, STM32F401, RP2040), and others. Split keyboard support with serial and I2C communication between halves. Audio feedback via piezo buzzer with musical notes. Mouse key emulation. Stenography (Plover) support. QMK Toolbox GUI tool for flashing firmware. QMK Configurator web interface for creating keymaps without coding. Bluetooth support for wireless keyboards. Open source under GPL-2.0.