Fitts's Law
The time to hit a target shrinks with its size and grows with distance to it — so make frequent targets big and close.
Fitts's Law is a model from experimental psychology (Paul Fitts, 1954) predicting how long a pointing movement takes as a function of the target's size and its distance from the starting point. Formally, movement time scales with the log of distance over size — but the design consequence is simpler than the math: a button you want people to hit often and hit fast should be large and near wherever their pointer already is.
The clearest applications are the ones users never notice working. The screen edges and corners are effectively infinite in size, because the pointer stops at the boundary regardless of overshoot — which is why macOS puts the menu bar at the very top and why a browser's maximize button lives in the corner rather than a few pixels inset. A context menu that opens exactly under the cursor is exploiting the same law: distance to the first item is near zero.
It also explains why a small, rarely-used icon (say, a settings gear) is an acceptable design even though it violates the "make it big" instinct — the law is about time cost, and infrequent targets can absorb some cost. The failure mode is applying that logic backwards: shrinking a primary action, or a mobile tap target, because it "looks cleaner," while ignoring that the people using it hit it dozens of times a day. Touch interfaces raise the stakes further, since a finger is a blunter instrument than a cursor and the effective minimum size for reliable hits is larger than most visual designers expect.
Fitts's Law pairs naturally with Hick's Law — one governs how long it takes to move to a choice, the other how long it takes to decide among choices — and together they cover most of the time-cost side of interaction design.
See also13
Affordance
A property an object's design communicates about how it can be used, before any instruction is read.
Design & Interface12 connections
Progressive Disclosure
Show only what most users need now, and defer the rest behind an explicit action, instead of exposing everything at once.
Design & Interface17 connections
Keyboard Navigation
Making every interactive affordance reachable and operable without a pointer.
Design & Interface34 connections
Gestalt Principles
A set of perceptual rules describing how the eye groups discrete elements into wholes before conscious analysis begins.
Design & Interface12 connections
Slider
A control that sets a value by dragging a handle along a track, borrowed from the faders of audio equipment, ideal for adjusting something approximate with instant feedback and poor for entering an exact number.
Design & Interface11 connections
Call to Action
The button or link that asks a visitor to take the next step, such as signing up or buying, whose wording, prominence, and placement are heavily tested and easily turned manipulative.
Design & Interface9 connections
Tiling Window Manager
A window manager that arranges windows automatically into non-overlapping tiles and is driven mainly from the keyboard, trading freeform placement for zero layout effort.
Design & Interface11 connections
Bottom Sheet
A panel that slides up from the bottom of a phone screen to show extra content or choices, often draggable between heights, placed where thumbs can reach it on large phones.
Design & Interface13 connections
Pointer Events
The browser's unified model for input from a mouse, a finger, or a pen, delivering one set of events with details such as pressure and contact size, which replaced separate and incompatible mouse and touch event systems.
Web Platform8 connections
Dropdown Menu
A control that hides a list of options until it's opened, saving space at the cost of hiding choices, which ranges from desktop menu bars to the web's notoriously hard-to-style select element and the sprawling mega menus of retail sites.
Design & Interface17 connections
Direct Manipulation
Ben Shneiderman's 1983 name for interfaces where people act on visible objects with immediate, reversible feedback, such as dragging a file or resizing a shape, instead of typing commands that describe the change.
Design & Interface14 connections
Layout Shift
Visible content jumping position after it first appears, usually because something loaded late without reserved space, measured by browsers as Cumulative Layout Shift.
Web Platform12 connections
Context Menu
A menu of actions for the thing under the pointer, opened by right-click or long press, which saves travel and narrows choices but is invisible until summoned, so it should never be the only route to an action.
Design & Interface12 connections
Linked from13
- AffordanceDesign & Interface
A property an object's design communicates about how it can be used, before any instruction is read.
- Bottom SheetDesign & Interface
A panel that slides up from the bottom of a phone screen to show extra content or choices, often draggable between heights, placed where thumbs can reach it on large phones.
- Call to ActionDesign & Interface
The button or link that asks a visitor to take the next step, such as signing up or buying, whose wording, prominence, and placement are heavily tested and easily turned manipulative.
- Context MenuDesign & Interface
A menu of actions for the thing under the pointer, opened by right-click or long press, which saves travel and narrows choices but is invisible until summoned, so it should never be the only route to an action.
- Dark PatternDesign & Interface
An interface deliberately designed to steer users toward a choice that serves the business rather than the user.
- Direct ManipulationDesign & Interface
Ben Shneiderman's 1983 name for interfaces where people act on visible objects with immediate, reversible feedback, such as dragging a file or resizing a shape, instead of typing commands that describe the change.
- Dropdown MenuDesign & Interface
A control that hides a list of options until it's opened, saving space at the cost of hiding choices, which ranges from desktop menu bars to the web's notoriously hard-to-style select element and the sprawling mega menus of retail sites.
- Hick's LawDesign & Interface
Decision time rises with the number and complexity of choices offered, roughly logarithmically — fewer options decided faster.
- Layout ShiftWeb Platform
Visible content jumping position after it first appears, usually because something loaded late without reserved space, measured by browsers as Cumulative Layout Shift.
- Pointer EventsWeb Platform
The browser's unified model for input from a mouse, a finger, or a pen, delivering one set of events with details such as pressure and contact size, which replaced separate and incompatible mouse and touch event systems.
- Progressive DisclosureDesign & Interface
Show only what most users need now, and defer the rest behind an explicit action, instead of exposing everything at once.
- Tiling Window ManagerDesign & Interface
A window manager that arranges windows automatically into non-overlapping tiles and is driven mainly from the keyboard, trading freeform placement for zero layout effort.
- Touch Target SizeDesign & Interface
How large a tappable element needs to be for fingers to hit it reliably, roughly 44 to 48 points, and why the visible icon can be smaller than the area that responds.