In most circumstances, you can get the width of the terminal window using the comamnd tput cols. However I discovered that this doesn’t quite work as expected if you try it as part of your status-right or status-left configuration (and pretty much in any other format strings in tmux.) I tried to implement something that auto-hides certain items on my status-line when the iTerm2 narrows down to a particular size, but tput cols always return the value 80.

To properly get the window width, you will need to use the window_width property that is available in all format strings:

#!/usr/bin/env zsh

local window_width=$(tmux display-message -p "#{window_width}")

# Only attach certain items if window width is greater or equal to 180 columns
if [[ $window_width -ge 180 ]]; then
 ...