A split button separates default and overflow onto body and chevron

What it is

A split button looks like one button and is two regions: a large body that immediately runs the default (Save), and a small chevron that opens an overflow (Save as, Export). It splits “the usual one hit” from “occasional relatives”: not a menu button that must open every time, and not a group that lays every relative on the surface.

Why it happens

The default gets primary area and one click; rare variants are a second target, trading an extra click for width. People have to learn “this piece does it, that piece asks again.” Learning needs a visible seam and two hit regions. Without a seam the whole control is taken as a menu button or as a single action—clicking the body pops a menu, or clicking the chevron saves at once. The default must actually be frequent: if the body runs a rare item, people detour to the chevron every time and the split becomes a clumsy menu button. Menu items should be variants of the same verb, not a drawer of arbitrary commands, or the chevron is a hamburger.

Studying it

Compare three controls for Save and Export: a split button, a menu button that always opens, three independent buttons. Log whether the chevron is found on the first try, and whether the default is mistaken for a menu.

Independent variables: visible seam, whether the default is truly frequent, whether the chevron has words. Dependent variables: time to discover overflow, body taken as menu, chevron taken as default.

Internal users already know Save as sits behind the chevron, so discovery is overestimated. Use people who have never seen that split for a first Save.

Where it stops holding

Do not split a single action; the chevron becomes a lie. On touch, two hit regions are hard to make large enough; a separate Save plus More is often better. If the last choice is remembered as a new default, the body’s meaning drifts across users; do not silently retarget the default in a collaborative setting.

Applying it

• Label the body with the default action itself (Save), not “Save…” which suggests another question.
• Draw a visible seam between body and chevron, and fire two independent activations.
• Put only variants of that verb in the menu; do not stuff settings and delete.
• Verify by asking someone new to save once and export once. If the first body click pops a menu, or Export cannot be found, the two parts are not separated.

Related

• Within the group: E1.14.1 A button group presents related actions that are exclusive or parallel · E1.14.3 A too-small chevron on a split button misses into the menu · E1.14.4 Too many items in a group should become another control, not a longer row
• Adjacent: E5.12 Menus and submenus · E1.01 Button hierarchy · E1.05 Floating action buttons
• Search terms: split button · menu button · default action