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Action

Split button

A button for the most common action, joined to a small arrow button that opens related actions.

Also known as

Combo button — Carbon Design System

How to recognize it

One button divided in two: a labeled main part and a narrow part with a downward arrow, separated by a thin line.

Behavior

Pressing the main part runs the default action right away.
Pressing the arrow opens a menu of other actions; choosing one runs it and closes the menu.
The two parts are separate buttons, each reached with Tab.

Keyboard

Key	Action
`Tab`	Moves between the main button and the arrow button.
`Enter / Space`	On the main button, runs the default action. On the arrow, opens the menu and focuses the first item.
`↓ / ↑`	On the arrow, opens the menu. In the menu, moves between items.
`Esc`	Closes the menu and returns focus to the arrow button.

Menu: A split button runs its main action with one press and keeps the rest in a menu; a menu button only opens the menu.
Button: A button offers one action; a split button adds a menu of related actions beside it.

Sources

Carbon Design System: Menu buttons (Combo button) (Last checked: 2026-10-20)
MUI: Button Group (Split button) (Last checked: 2026-10-20)
WAI-ARIA APG: Menu Button Pattern (Last checked: 2026-10-20)