i3-nagbar

Display an error

$ i3-nagbar [[-m|--message]] "[error message]"

$ i3-nagbar [[-t|--type]] warning [[-m|--message]] "[warning message]"

$ i3-nagbar [[-f|--font]] "[pango:monospace bold 9]" [[-m|--message]] "[error message]"

$ i3-nagbar [[-b|--button]] "[button text]" [command] [[-m|--message]] "[error message]"

$ i3-nagbar [[-B|--button-no-terminal]] "[button text]" [command] [[-m|--message]] "[error message]"

$ i3-nagbar [[-pm|--primary --message]] "[error message]"

i3-nagbar [-h | -v | -m message | -T title | -t timeout | -c close-text]

-h, --help
    Display help message and exit.

-v, --version
    Display version information and exit.

-m message, --message=message
    Main message text to display in the bar (required for display).

-T title, --title=title
    Optional title text above the message.

-t timeout, --timeout=timeout
    Auto-dismiss after timeout ms (default: 10000; 0 disables).

-c close-text, --close-text=close-text
    Text on the close button (default: "Close").

i3-nagbar is a lightweight utility from the i3 tiling window manager that displays a semi-transparent bar at the top of the screen. It shows a user-defined title and message, along with a close button, ideal for notifying about urgent windows or events.

Commonly configured in i3's config file using for_window [urgent] exec i3-nagbar ..., it pops up when applications mark windows as urgent (e.g., flashing terminals with errors). The bar remains until closed manually or timed out, helping users not miss important alerts in a minimalistic WM environment.

Customizable via options for message, title, timeout, and button text, it integrates seamlessly with i3's keyboard-driven workflow. Clicking the bar or button dismisses it without additional actions, relying on i3 bindings for handling urgents like i3-msg [urgent] focus. Simple, non-intrusive, and X11-specific.

Requires i3 window manager; bar fixed at screen top; no click actions beyond close; X11-only, not Wayland-compatible.

In ~/.config/i3/config:
for_window [urgent] exec --no-startup-id i3-nagbar -t 2000 -m 'You have {{id_label}} urgent windows.'

Supports Pango markup in texts for formatting; multiple invocations stack vertically; uses i3's font config.

Developed by Michael Stapelberg for i3wm around 2010; stable since early i3 versions (pre-4.x); remains in current releases (4.22+) for legacy urgent notifications.

i3(1), i3-msg(1), i3bar(1)