Toggle between pane layouts
panes
// what it does
Ctrl+b Space cycles through tmux's five preset layouts — even-horizontal, even-vertical, main-horizontal, main-vertical, and tiled — rearranging your existing panes into each. It's the quickest way to reflow a messy set of splits into something orderly. Each press advances to the next layout in the list.
// shortcut
Ctrl + bSpacebar
// gotcha
Switching layouts discards any manual pane resizing, snapping everything back to the preset's proportions. The main-* layouts hand the first pane a large "main" area, which surprises you if you expected equal sizes.