Emacs: Key Notation: Return, Tab, Escape

2023-09-16 note: this page is obsolete. Emacs 29 (Released 2023-07) has made many changes in key syntax.

<return> vs RET

"<return>" is the Return key while emacs runs in a graphical user interface.

"RET" is the Return key while emacs runs in a terminal.

"RET" is also equivalent to "C-m" (Ctrl+m). 〔see Emacs Key Syntax Explained〕

if you define:

(global-set-key (kbd "<return>") 'backward-char)

and run emacs in terminal, your keybinding will have no effect.

you need to use:

(global-set-key (kbd "RET") 'backward-char)

But the problem is, by binding (kbd "RET"), you are also binding (kbd "C-m"), regardless you run emacs in terminal or GUI.

<tab> vs TAB

• "<tab>" is the notation for Tab key when emacs is run in graphical user interface. If you define a key with <tab>, it has no effect in terminal.
• "TAB" is the notation for Tab key when emacs is run in terminal. "TAB" is also equivalent to "C-i", in both graphical user interface and terminal. If you define key by "TAB", it also defines "C-i" (and vice versa), in both graphical user interface and terminal.

<escape> vs ESC

• "<escape>" is the notation for Escape key when emacs is run in graphical user interface. If you define a key with <escape>, it won't have effect in terminal.
• "ESC" is the notation for Escape key when emacs is run in terminal. "ESC" is used in text terminal to communicate many special keys.
• Also, "ESC" is the same as "C-[".

WARNING: Binding ESC may make arrow keys or f1 f2 keys not work, in text terminal, or in text terminal and running a remote emacs because text terminal relies on escape sequence to represent those keys.