The consideration of which screen zones are comfortably reachable by the thumb when a device is held one-handed, typically modeled as a 'thumb zone' arc across the lower portion of the screen. Thumb reachability guides the placement of frequently used actions within easy reach and relegates less critical or infrequent actions to harder-to-reach upper corners.
Common contexts
- Positioning a primary action button in the lower center of a mobile screen during layout review
- Relocating a destructive delete action to an upper corner specifically to reduce accidental taps
- Auditing a navigation bar redesign to ensure the most-used tabs sit within the natural thumb arc
Use when
Apply thumb reachability thinking whenever you're placing interactive elements on a mobile screen — particularly for actions users will trigger repeatedly or in motion, like send, next, or confirm. The lower 40% of the screen is premium real estate; justify anything you put in the top corners.
Avoid when
Don't let thumb zone models override all other layout decisions — two-handed tablet interactions, landscape orientation, and assistive device users all have different reach patterns. Designing exclusively for right-handed one-handed phone use ignores a meaningful portion of your audience.
The real value of thumb zone models isn't the diagram — it's the conversation it starts with PMs who keep asking for primary CTAs at the top of the screen because 'that's where users look first'.
Real-world examples
- Spotify moved their playback controls from the top of the screen to a persistent bottom bar when their own thumb-reachability research showed that 73% of interactions occurred in the bottom third of the display.
- Apple's Reachability feature (double-tap home button to pull the screen down) acknowledges that the iPhone 6+'s 5.5-inch screen makes the top of the screen unreachable for single-handed use — a workaround built into the OS.
- Google Chrome moved the URL bar from top to bottom of the screen in their mobile redesign after eye-tracking and tap-accuracy data showed users mismatch tapped on the top bar 3× more often than the bottom bar on phones over 5 inches.