Best practices designers can consider when building user interfaces.

The Laws of UX are a collection of psychology-based principles that describe how people perceive, think about and interact with user interfaces. They fall into four groups — heuristics, Gestalt principles, cognitive biases and general principles — and give designers research-backed reasons for their design decisions. Each law distils a finding from psychology or cognitive science into a practical guideline for building clearer, more usable products.

This reference covers 30 Laws of UX, spanning classic heuristics such as Fitts’s Law, Hick’s Law and Jakob’s Law, Gestalt grouping principles, cognitive biases like the Aesthetic-Usability Effect and Peak-End Rule, and broader principles including Cognitive Load and Working Memory. The set has grown over time as newer principles — such as the Paradox of the Active User and Selective Attention — have been added.

The Laws of UX are organised into four categories. Heuristics are practical rules of thumb that speed up decisions (e.g. Hick’s Law). Gestalt principles describe how the eye groups visual elements (e.g. Law of Proximity). Cognitive biases are systematic patterns in judgement (e.g. Von Restorff Effect). General principles cover foundational ideas about how the mind handles information (e.g. Cognitive Load).

The Laws of UX matter because they ground design choices in how people actually think and behave rather than in personal taste. Applying them helps designers reduce cognitive load, guide attention, make interfaces feel familiar, and create experiences people find intuitive. They also give teams a shared vocabulary for explaining and defending design decisions during reviews and usability testing.

A heuristic is a practical rule designers apply on purpose to make an interface easier to use, such as keeping the number of choices small. A cognitive bias is an unconscious tendency in how users judge or perceive things, such as assuming an attractive interface is easier to use. In short: heuristics are guidelines you design with, while cognitive biases are behaviours you design around.

The best way to learn the Laws of UX is to study each principle, then practise applying it to real interfaces through hands-on projects and feedback. The Institute of Digital Marketing New Zealand (IDNZ) runs an Agile Product Design Expert certification that teaches UX psychology, research and interface design in a structured, mentored programme — turning these principles into a repeatable design practice.