i3wm: How to move workspaces between monitors?

You can define a binding in your i3 config. Note: windows are called "containers", and monitors are called "outputs".

move workspace to output left|right|down|up|current|primary|<output>

Here's what I use in my config:

# move focused workspace between monitors
bindsym $mod+Ctrl+greater move workspace to output right
bindsym $mod+Ctrl+less move workspace to output left

Strangely, I'd expect the $mod+Ctrl+greater to require me to hit Ctrl and Shift at the same time, since you need to press Shift to type < and >. However, pressing just mod, Ctrl, and , works, which is very nice.

Note, you can also set a keybinding to send things to a specific monitor by its name.

The workspace can be explicitly specified by name like this, for values of workspace_name and output_name:

i3-msg '[workspace="workspace_name"]' move workspace to output output_index

Note that if you name your workspaces like 1:first, you use 1 not first.