ux-laws

Laws of UX — Knowledge Base

A collection of 30 UX laws and psychological principles that designers and developers should consider when building user interfaces. Based on https://lawsofux.com/ by Jon Yablonski.

How to use

This skill functions as agentic RAG — the agent navigates the sections hierarchy, loading only the laws relevant to the current task.

Step 1 — Identify the UX concern

What you need to check	Start here
Too many options in UI (dropdowns, menus, nav)	Heuristics → Hick's Law, Choice Overload
Touch targets too small or poorly spaced	Heuristics → Fitts's Law
Response time / loading issues	Principles → Doherty Threshold
Too much info on screen at once	Cognitive → Miller's Law, Cognitive Load, Chunking
Grouping / layout / spacing problems	Gestalt → Proximity, Similarity, Common Region, Uniform Connectedness, Prägnanz
Users confused by unfamiliar patterns	Principles → Jakob's Law; Gestalt → Mental Model
Visual hierarchy / what stands out	Cognitive → Von Restorff Effect, Serial Position Effect, Selective Attention
Forms too long or complex	Principles → Tesler's Law, Parkinson's Law
User motivation / progress	Principles → Goal-Gradient Effect, Zeigarnik Effect, Peak-End Rule
Input handling / error tolerance	Principles → Postel's Law
Simplicity vs. complexity trade-off	Principles → Occam's Razor, Tesler's Law, Pareto Principle
Onboarding / first-time users	Cognitive → Paradox of Active User, Working Memory
Overall UX review	Read Code Patterns for all code-level checks

Step 2 — Read the _index.md, then the specific law

1. Open the _index.md of the target section — it lists all laws with one-line summaries.
2. Read only the specific law file you need.
3. For code review, always also check sections/05-code-patterns/ for actionable rules.

Step 3 — Apply to code

When reviewing frontend code:

1. Identify which UX laws are relevant to the component/page
2. Check the code patterns section for specific violations
3. Provide actionable recommendations with code examples

Section INDEX

#	Section	Laws	When to use
01	Heuristics	4	Decision time, target acquisition, response time, user perception
02	Cognitive	10	Memory limits, attention, learning, cognitive biases
03	Gestalt	6	Visual grouping, layout, element relationships
04	Principles	10	Design trade-offs, simplicity, user motivation, input handling
05	Code Patterns	—	Concrete code-level checks mapped to UX laws

Quick Reference — All 30 Laws

Law	Category	One-liner
Aesthetic-Usability Effect	Heuristic	Beautiful design is perceived as more usable
Choice Overload	Heuristic	Too many options overwhelm users
Fitts's Law	Heuristic	Larger, closer targets are faster to acquire
Hick's Law	Heuristic	More choices = longer decision time
Chunking	Cognitive	Group info into meaningful chunks
Cognitive Bias	Cognitive	Systematic thinking errors affect decisions
Cognitive Load	Cognitive	Minimize mental effort to use interface
Miller's Law	Cognitive	Working memory holds 7±2 items
Paradox of Active User	Cognitive	Users skip manuals, learn by doing
Selective Attention	Cognitive	Users filter out irrelevant info
Serial Position Effect	Cognitive	First and last items remembered best
Von Restorff Effect	Cognitive	Distinctive items stand out in memory
Working Memory	Cognitive	Limited capacity for active info
Flow	Cognitive	Optimal state of focused engagement
Law of Common Region	Gestalt	Shared boundaries group elements
Law of Proximity	Gestalt	Near elements are perceived as grouped
Law of Prägnanz	Gestalt	We simplify complex shapes mentally
Law of Similarity	Gestalt	Similar elements are seen as related
Law of Uniform Connectedness	Gestalt	Connected elements are perceived as related
Mental Model	Gestalt	Users have prebuilt expectations
Doherty Threshold	Principle	System response < 400ms keeps flow
Goal-Gradient Effect	Principle	Motivation increases near the goal
Jakob's Law	Principle	Users expect your site to work like others
Occam's Razor	Principle	Simplest solution is usually best
Pareto Principle	Principle	80% of effects from 20% of causes
Parkinson's Law	Principle	Tasks expand to fill available time
Peak-End Rule	Principle	Experiences judged by peak + end moments
Postel's Law	Principle	Accept varied input, send strict output
Tesler's Law	Principle	Complexity can be moved but not removed
Zeigarnik Effect	Principle	Incomplete tasks are remembered better