thumbaccessible

Thumbaccessible is a term used in user experience design to describe interfaces that are comfortably operable with the thumb when a device is held in one hand. The concept focuses on one-handed usability and accessibility, aiming to reduce the need for two-handed interaction and to accommodate users with varying hand sizes and dexterity.

Core principles include placing primary actions within the natural thumb reach zone, typically toward the lower portion of the screen, while keeping other controls accessible without excessive finger travel. Touch targets should be large enough and spaced adequately, with clear visual contrast. Designs should be usable for both left- and right-handed users, and consider features that enable one-handed operation, such as bottom navigation, bottom sheets, and floating action buttons anchored to a thumb-friendly area. It is also advisable to minimize tasks that require reaching to the top corners or precise taps.

Techniques commonly used to achieve thumb accessibility include implementing bottom navigation bars, persistent action bars near the bottom, and contextual menus that can be reached without scrolling. Interfaces may offer a one-handed mode that shifts or scales controls downward, and responsive layouts that adjust based on grip style. Consistent typography and sufficient tap target sizes (for example, around 44 by 44 dp in many guidelines) support easier thumb interaction.

Measurement and testing of thumb accessibility typically involve reachability assessments on a range of device sizes, usability testing with participants of various hand sizes, and checks for left- and right-handed use. Thumbaccessible aligns with broader usability and accessibility goals, drawing on ergonomic principles and existing platform guidelines without constituting a formal standard.