Fitts's Law
Big targets that are close are fast to hit. Small targets that are far away get missed.
What it is
The time to reach a target depends on its size and distance. On screens this means primary actions should be large and near where the pointer or thumb already is, and destructive actions should be neither.
The research
Movement time to a target increases with distance and decreases with target width, following a logarithmic relationship that has held across pointing devices for seventy years.
Fitts, 1954
How to use it
Thumb-zone the primary button
On mobile, the main action lives at the bottom of the screen, full width.
Make the whole card clickable
If a card links somewhere, the entire card is the target, not the 12px title.
Shrink the escape hatch
Cancel, delete and unsubscribe are text links, not buttons, and never sit beside the primary action.
Related
Sources that shaped this entry: growth.design.