Key/Meta

• Meta (M-)

  • Modifier key that in modern terminals maps to Alt/Option; used pervasively in Emacs, tmux, and readline for single-keystroke commands.

  • Larger Context

    • Origin

      • The Meta key originated on Unix/Lisp-machine keyboards (Sun, Symbolics). No modern keyboard has a physical Meta key; terminal emulators map it to Alt or Option.

    • macOS mapping

      • Option (⌥) — the correct Meta key in terminal emulators (iTerm2, Kitty, Alacritty, WezTerm). Requires configuration: in iTerm2, set Left Option key → Esc+.
      • Command (⌘) — a macOS-only UI modifier; terminal apps do not see it as Meta. Most Cmd+ combos are intercepted by the OS before reaching the terminal.

    • Notation

      • Notation	Meaning
        M-x	Meta+x (press Alt/Option+x, or press Esc then x)
        ESC x	Meta+x as two separate keystrokes (fallback when Option isn't forwarded as Esc+)

    • Related modifier keys

      • Key/Super — maps to Command (⌘) on macOS, Windows key on Linux/Windows. Used in GUI window managers and Emacs (s-).
      • Key/Hyper — a fourth modifier from the Lisp-machine era; rarely present on modern hardware. Some Emacs users remap Caps Lock to Hyper (H-).
      • Key/Control — standard Ctrl modifier across all platforms (C-).
      • Key/Alt — on Linux/Windows, Alt is Meta in terminals. On macOS, Alt ≈ Option and serves as Meta when configured.

    • Where M- appears

      • tmux — bind-key -T prefix M-1 through M-7 select pane layouts.
      • Emacs — pervasive M-x, M-f, M-b, etc.
      • Readline/shell — M-f (forward word), M-b (backward word), M-. (insert last argument).