Vim 101: What is the Leader Key?

You’re happily using Vim, slowly mastering file navigation, split windows and tabs, search and replace, and then you discover a hot new .vimrc on Hacker News that includes lots of commands like this:

noremap <Leader>W :w !sudo tee % > /dev/null

What the devil is <Leader>? Well, in this example it simply means typing \W (backslash then w) in Normal mode will save the current file using the sudo command. Does that mean <Leader> means backslash? Well, not quite. The <Leader> key is a reference to a specific key defined by the mapleader variable. A lot of people change to comma because they find it easier to type:

let mapleader=","

The mapleader variable is easy to change, and if you always remember to map keys with <Leader> then you'll avoid confusing your own customisation with Vim's default keyboard shortcuts.

The beauty of the <Leader> key is it effectively gives us a namespace for customised keyboard shortcuts. You don't need to worry about treading on Vim's toes when you set a keyboard shortcut using <Leader>.

Vim waits for 1000 milliseconds after the <Leader> key has been pressed, so if you take too long to press the next key in the sequence it won't be matched. This timeout can be changed by using :set timeoutlen to set specific value.