tmux/Option/pane-border-lines

• pane-border-lines

  • Selects the characters used to draw pane borders.

  • Values

    • single — single ACS or UTF-8 lines.
    • double — double UTF-8 lines.
    • heavy — heavy UTF-8 lines.
    • simple — ASCII lines.
    • number — pane numbers.
    • spaces — space characters.
    • none — no border for floating panes.
  • double and heavy fall back to ACS line drawing when UTF-8 is unavailable.