Start

Thumb-zone CTA

Effort: Low

What to notice

A comfortably large button stays fixed at the bottom of a phone screen.

How to build it

  1. Pin the main action to the bottom and make it at least 48px tall.
  2. Pin only one button so reading is not obstructed.
  3. Hide it while the keyboard is open or the user is typing.

Measure

Main metric
Mobile CTA click-through rate
Guardrail
Back navigation after accidental taps

When it backfires

A pinned button that covers text or links makes the page harder to read.

Theory behind it

Fitts’s law

The farther and smaller a target is, the longer it takes to hit.

Well supported

Fogg Behavior Model (B=MAP)

A behavior happens when motivation, ability, and a prompt meet at the same moment.

Practitioner framework