Interaction & Speed
Fitts's Law
The time it takes to move to and select a target is a function of the target's size and the distance to it: bigger, closer targets are faster and easier to hit.
Mechanism
Why it happens
Pointing is a closed-loop motor task: the smaller or farther the target, the more corrective micro-movements it takes to land on it.
Impact
Why it matters
- Primary actions placed far from the last touch point cost real time and error rate
- Small tap targets are the single most common source of mis-taps on mobile
- Distance matters as much as size. A huge button in the wrong corner is still slow to reach
Example
Without vs. with
Primary "Save" is a 28px link in the top-right corner while the cursor is in a form field at the bottom of a long page.
Primary "Save" is a 44px button pinned near the active form area, sized larger than any secondary action.
Checklist
How to apply it
Give primary actions a minimum 44×44px hit target
Place the primary action close to where attention (and the cursor or thumb) already is
Make destructive or rare actions smaller and farther away, not just differently coloured
On mobile, keep primary actions within thumb reach in the lower two-thirds of the screen
Where it shows up