Tmux is a fantastic tool for improving productivity when working with a terminal. One of the first things people configure when start using tmux is changing the prefix key. The default value is control+b, which is not very confortable to press with a single hand. And as you’ll end up pressing it a lot, for every tmux command, the most common used configuration is changing it to control+a.

This is much better, but you still need to press two keys simultaneously before typing any tmux command. After using this configuration for some time, I decided to change it to a single key, to make it even easier.

I though about changing the prefix to caps lock. Besides being rarely used, it’s very well positioned. However, you can’t set caps lock as prefix in tmux. An alternative solution is mapping the caps lock key to something else. In OSX, you can set it to another modifier key, like control, shift or esc: go to System Preferences => Keyboard => Modifier keys. First I tried mapping it to esc, and setting esc as tmux prefix. It works, but this setup brought another problem: as a vim user, I use the esc key a lot (to alternate between vim modes), so now I had to type esc/caps lock twice to send the esc key to vim. It was ok, but not ideal.

Then I tried another solution: I installed Karabiner-Elements, a Mac app which allows you to completely customize your keyboard. So I mapped the caps lock key to Home (which doesn’t exist in Mac keyboard), and changed tmux prefix key to Home:

set -g prefix Home
unbind C-b
bind-key Home send-prefix

Now I have a great configuration: I use a single key (caps lock) as prefix, and without losing any key functionality.