Which placement of the action button is better: in the center of the screen or at the right edge? (mobile interface)

For mobile interfaces, it is better to place the action button at the right edge of the screen, especially if it is the primary and frequently used one.

Reasons:

• Most users are right-handed, and it is more comfortable for them to reach the right edge with their thumb.
• The button at the edge of the screen is more accessible when using one hand.
• The center of the screen is often occupied by content, and a button at the edge does not obscure important elements.

However, if the interface is designed for left-handed users or has other UX features, the placement may vary. Generally, the standard is to place the action button in the bottom right corner (Floating Action Button).