interaction design
Fitts's law
What is Fitts's law?
The time it takes to hit a target grows as it gets smaller or farther away. Large, nearby targets are fast to hit; small, distant ones take longer.
Also known as: Fitts' law, Fitts law
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The demo
Ten rounds. A target appears - click or tap it as fast as you can. They alternate big and small, near and far, and every hit is timed.
What this demo shows (text version)
This is a pointing game: a button appears in a random spot and you hit it as quickly as you can, ten times, with the button alternating between large and small and near and far. It times your reaction-and-movement for each hit.
The reliable result: people hit the big, near targets noticeably faster than the small, far ones - markedly slower on the small, distant ones. That difference is Fitts's law. It's the evidence behind making important buttons large and placing them close to where the cursor already is, and behind parking risky actions in small, out-of-the-way controls.
How quickly someone can reach a target depends on its size and distance - bigger, closer targets are faster and easier. That’s why primary actions should be large and easy to reach, and why tiny buttons slow people down - you can see this in action right here.
That gap you just felt is Fitts's law. It's why the primary button is big and close, and the "delete account" link is small and tucked away in a corner.
Designers quote Fitts's law to justify big buttons, then forget its other half: distance. A huge "Save" is still slow if it's marooned in the opposite corner from where the cursor already is.
The cheat codes are the screen edges and corners - the pointer stops dead against them, so they behave like infinitely large targets. That's why the macOS menu bar sits flush to the very top. Spend that free real estate on the things people reach for most.