What is Interaction design?
Interaction design (IxD) is the design of the dialogue between a user and a product, defining how the product behaves in response to user actions through sequences, transitions, feedback, and state changes.
How it works
Interaction design focuses on five dimensions: words (labels, instructions), visual representations (icons, images, typography), physical objects (hardware, touch surfaces), time (animation, duration, sequence), and behavior (how the product responds to input). Key principles include providing immediate feedback for every action, maintaining predictable behavior, offering undo for reversible actions, and matching the pace of interaction to the user’s cognitive speed. IxD overlaps with but is distinct from UI design (visual appearance) and UX design (holistic experience); it specifically concerns the behavioral layer of how things respond.
Applied example
When a user drags a file to the trash on macOS, the interaction design includes: the file icon attaching to the cursor (feedback that drag is active), the trash icon enlarging as the cursor approaches (feedforward showing the drop target will accept), the file disappearing with a paper-crumpling sound (confirmation), and the option to undo immediately (error recovery). Each micro-interaction was deliberately designed.
Why it matters
Interaction design shapes the moment-to-moment experience of using a product, determining whether it feels responsive, predictable, and natural or laggy, surprising, and frustrating.
