How do I change the tmux prefix keyboard shortcut from ctrl+B to space+B while, by default, the space button has a command?

2 Answers 2


From tmux man page:

tmux allows a command to be bound to most keys, with or without a pre-fix key. When specifying keys, most represent themselves (for example ‘A’ to ‘Z’). Ctrl keys may be prefixed with ‘C-’ or ‘^’, and Alt (meta) with ‘M-’.

Which means you can bind Ctrl and Alt as prefix keys - not space. Actually, I don't know any app that let's you bind space as a prefix key, but please enlighten me.

To bind another key as tmux prefix key, add the following to .tmux.conf (for Alt+X as prefix key):

set -g prefix M-x
bind M-x send-prefix
  • Well, now that there is no way to set the space, how do I set the Alt and x + % buttons to halve the screen vertically? Alt + x + %
    – M UBU 2020
    Commented Jul 28, 2020 at 12:46
  • Are you using Alt+X as tmux prefix key then? Answer edited above. Commented Jul 28, 2020 at 12:49
  • My tmux version is tmux 3.0a But I did not find a file called .tmux.conf Can this method >>(set -g prefix M-x bind M-x send-prefix)<< be adjusted by typing <command prompt> in tmux itself?
    – M UBU 2020
    Commented Jul 28, 2020 at 13:29
  • Yes I believe so. But maybe you have to create the .tmux.conf file first if it's not in your user dir, makes things much easier. Commented Jul 28, 2020 at 13:49

I've set mine to Ctrl-Space. This works really well. I imagine other combinations with Space will work as long as it's the second character in the chain.

In your config you can

unbind C-b
set -g prefix C-Space
bind Space send-prefix

This will:

  1. Unbind the default C-bprefix
  2. Set C-Space to the new prefix
  3. And ensure any presses to Space get passed to the active pane

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