KeyRemap4MacBook

KeyRemap4MacBook is a macOS keyboard remapping utility that allows users to redefine keys, create complex key sequences, and assign different mappings depending on the active application or keyboard layout. It runs as a background process and uses a plain text configuration file to store rules, enabling users to modify how input is interpreted at the system level. The software supports remapping individual keys, altering modifier behavior, and creating conditional mappings that respond to the current application or input state, including accommodations for non-US layouts such as Japanese keyboards.

The tool is popular among power users who need granular control over keyboard behavior, including common remaps like swapping Caps Lock and Escape or reassigning function keys for development and gaming workflows. Its configuration language is designed to be human-readable, permitting single-key remaps, multi-key sequences, and chord-like combinations.

History and development: KeyRemap4MacBook originated in the open-source community to provide enhanced keyboard customization on macOS. In the mid-2010s, development shifted toward Karabiner, and later Karabiner-Elements was introduced to support newer macOS versions and revised security models. The project’s influence persists in the ecosystem, with Karabiner-Elements continuing the legacy through active maintenance and ongoing updates.

See also: Karabiner, Karabiner-Elements.