DECSET ?1004 — Focus in/out events

Make the terminal report when its window gains or loses keyboard focus.

Byte forms

Every common string-literal form so you can paste-and-search either direction.

\\x1b[\x1b[?1004h (enable) \x1b[?1004l (disable)

\\033[\033[?1004h / \033[?1004l

\\e[\e[?1004h / \e[?1004l

ESC [ESC [ ? 1 0 0 4 h / l

hex1b 5b 3f 31 30 30 34 68 / 6c

Description

When enabled, the terminal sends `\x1b[I` to stdin whenever the window gains focus and `\x1b[O` whenever it loses focus. TUIs use this to pause animations, redraw their status bar, or refresh data when the user returns. Vim's `FocusGained` / `FocusLost` autocommands and tmux's `focus-events on` rely on this. Always disable (`?1004l`) on exit; otherwise a crashed TUI keeps spraying `^[[I` / `^[[O` into the user's shell every time they alt-tab.

Spec citation: xterm-ctlseqs (Private mode 1004)

Examples

bash

printf '\033[?1004h'   # enable focus events\n# (when window focus changes, terminal emits \x1b[I or \x1b[O)

python

import sys; sys.stdout.write('\x1b[?1004h')

fmt.Print("\x1b[?1004h")

javascript

process.stdout.write('\x1b[?1004h')

printf("\x1b[?1004h");

Terminal support

xterm: yes
Linux console (fbcon): no
macOS Terminal.app: no
iTerm2: yes
Windows Terminal: yes
cmd.exe / ConPTY: no
kitty: yes
alacritty: yes
WezTerm: yes
Ghostty: yes
GNOME Terminal: yes
Konsole: yes
tmux: no
GNU screen: no

xterm	Linux console (fbcon)	macOS Terminal.app	iTerm2	Windows Terminal	cmd.exe / ConPTY	kitty	alacritty	WezTerm	Ghostty	GNOME Terminal	Konsole	tmux	GNU screen
yes	no	no	yes	yes	no	yes	yes	yes	yes	yes	yes	no	no

Related sequences

In the family cookbook

DEC cookbook · 6. Focus events & sync update — `?1004`, `?2026`