thumbonly

Thumb-only is a term used in human-computer interaction and mobile user experience to describe interfaces and interaction patterns that are fully usable with one hand, typically using the thumb. The concept is informal and used in design discussions to emphasize reachability, comfort, and ease of use on handheld devices.

In practice, thumb-only design favors elements that can be accessed without shifting grip. This includes bottom-aligned controls, large tap targets, and gestures that can be performed within the thumb’s range. Many mobile platforms provide one-handed or reachability modes that shift or scale UI components toward the lower portion of the screen to accommodate thumb reach, enabling efficient navigation with a single hand or thumb.

Design considerations for thumb-only interfaces include device size and grip, screen orientation, and the distribution of controls. Key practices include placing primary actions within easy thumb reach, using bottom navigation or pill-shaped controls, ensuring targets meet minimum size requirements, and supporting reversible layouts for left- and right-handed use. Accessibility considerations also play a role, such as providing alternative input methods and ensuring comfortable reach for users with varied dexterity.

Thumb-only relates to concepts such as one-handed usability, reachability, and thumb typing. It is not a formal standard but a descriptive guideline found in style guides, design handbooks, and product documentation. Limitations arise on very large devices or in landscape orientation, where some tasks may require two-handed interaction or alternative input methods.