Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X. In addition to simple key remapping, it has special remapping modes like Emacs-mode, SandS-mode (Space and Shift).

Key Remapper is not available for Mac but there are some alternatives that runs on macOS with similar functionality. The best Mac alternative is Karabiner Elements, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Key Remapper and eight of them are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to Key Remapper are Kanata, Hyperkey, Ukelele and xmodmap.
Karabiner, previously called KeyRemap4MacBook, is a very powerful keyboard remapper for Mac OS X. In addition to simple key remapping, it has special remapping modes like Emacs-mode, SandS-mode (Space and Shift).

This is a cross-platform software keyboard remapper for Linux, macOS and Windows. A short summary of the features:
Use an additional modifier key for all your keyboard shortcuts with this straightforward app. Utilize an unused key by converting the caps lock or any modifier key to the hyper key, which combines all four modifiers. The hyper key can be used in any app with keyboard shortcuts.

Graphical tool for editing macOS keyboard layouts with drag-and-drop assignment of Unicode characters, creation of dead keys, mapping character strings, visual feedback, native .keylayout support, and easy customization for scripts or special input needs.

The xmodmap program is used to edit and display the keyboard modifier map and keymap table that are used by client applications to convert event keycodes into keysyms. It is a part of the X.Org project.
KeyBindingsEditor is a GUI-based editor for OS X key bindings. It allows for easy editing and supports single-action bindings (one action per keystroke), multi-action bindings (multiple actions for a keystroke) and Emacs meta binding-style multi-keystroke bindings.

PCKeyboardHack can change caps lock key behavior. For example, changing caps lock key to delete Key.

