# Laws Of UX > Apply the Laws of UX — psychology and Gestalt heuristics used as lenses on interface work. Use when designing or building any frontend a human will look at and use, when auditing or critiquing UX (heuristic evaluation, "is this good UX?", design review), or when a specific law is named (Hick's, Fitts's, Jakob's, Peak-End, the Gestalt grouping laws, …). - Skill: `imikailoby/laws-of-ux` (Agent Skill, multi-file: 2 files) - Install (CLI): `npx skillmds@latest add imikailoby/laws-of-ux` - Raw SKILL.md: https://api.skillmd.com/api/skills/imikailoby/laws-of-ux/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Web & Frontend - Author: imikailoby (https://skillmd.com/u/imikailoby) - Updated: 2026-09-17 - Page: https://skillmd.com/skills/imikailoby/laws-of-ux --- # Laws of UX Heuristic **lenses** for designing and critiquing interfaces. A lens is a default, not a mandate: apply the ones that fit, name each lens you use so feedback is concrete and teachable, and stay anchored to the user's actual goal — when their context or research contradicts a lens, the context wins; say so explicitly. Load `references/laws-catalog.md` for a law's full takeaways, examples, and origins — reach for it when a finding needs depth or the user asks why. ## Designing / building Pick the 3–5 lenses most relevant to the surface (a form → Tesler's, Postel's, Working Memory, Doherty; a landing page → Hick's, Von Restorff, Serial Position, Aesthetic-Usability) and let them shape the choices as you make them. Done when the delivered design names the lenses that shaped it. ## Auditing / reviewing Walk every group below. Cite a lens only where there's a real issue or a real win. Done when all six groups have been walked and every finding carries three parts: the law by name, a severity (critical / important / nice-to-have), and a concrete fix. ### Decisions & choices (reduce friction to act) - [ ] **Hick's Law** — Too many choices at once? Break into steps, group, defer. Decision time grows with number/complexity of options. - [ ] **Choice Overload** — Long undifferentiated lists (plans, products)? Add filtering, a recommended/featured default, side-by-side comparison. - [ ] **Miller's Law** — Are items chunked into ~5–9 groups rather than one flat dump? (Chunking guidance, not a quota — never cite "7±2" to justify an arbitrary limit.) - [ ] **Occam's Razor** — Can any element be removed without losing function? Remove it. Simplest sufficient design wins. - [ ] **Tesler's Law** — Irreducible complexity exists — is the *system* absorbing it, or is it dumped on the user (e.g. asking for data you could infer/autofill)? ### Targets & interaction (make actions easy to hit) - [ ] **Fitts's Law** — Are interactive targets large enough, well-spaced, and near the user's focus? Primary actions shouldn't be tiny or far. - [ ] **Postel's Law** — Inputs liberal in what they accept (phone/date formats, casing, whitespace), strict/clear in what they emit and validate? Forgiving + clear feedback. - [ ] **Doherty Threshold** — Feedback under ~400ms? Use optimistic UI, skeletons, progress, and perceived-performance tricks where work is slow. - [ ] **Flow** — Does the path keep the user in focused momentum (clear feedback, minimal friction), matching challenge to skill? ### Attention & emphasis (guide the eye) - [ ] **Von Restorff (Isolation) Effect** — Does the single most important action/element stand out visually — with one emphasis, not competing ones, and not styled like an ad? - [ ] **Selective Attention** — Anything important styled like/next to ads (banner blindness)? Any critical change that could go unnoticed (change blindness)? - [ ] **Serial Position Effect** — Are key items first/last in lists & nav (primacy/recency), least-important in the middle? - [ ] **Aesthetic-Usability Effect** — Is it visually polished? Pleasing design raises perceived usability and buys tolerance — and can mask real usability bugs in testing, so verify usability separately. ### Grouping & layout (Gestalt — structure perception) - [ ] **Law of Proximity** — Related things near each other; unrelated things spaced apart. Spacing communicates relationship. - [ ] **Law of Common Region** — Use a shared boundary/background (card, panel) to bind a group. - [ ] **Law of Uniform Connectedness** — Visually connect related controls (shared color/line/frame); connect with a line/arrow when showing relationships. - [ ] **Law of Similarity** — Similar appearance implies similar function; make links/nav visually distinct from body text. - [ ] **Law of Prägnanz** — Resolve ambiguity toward the simplest form; simple shapes are processed and remembered better. ### Memory & cognition (don't overload the user) - [ ] **Cognitive Load** — Cut extraneous load (decorative noise, irrelevant info); respect intrinsic load. Is every element earning its mental cost? - [ ] **Working Memory** — Recognition over recall: carry context across screens (breadcrumbs, visited states, comparison tables) so users never hold info in their head. - [ ] **Chunking** — Is content grouped into scannable, hierarchical modules (e.g. formatted phone/card numbers, sectioned forms)? - [ ] **Mental Model / Jakob's Law** — Does it match conventions users already know from other sites/apps? Innovate on value, conform on patterns. On big changes, let users opt into the new version. ### Motivation & memory of the experience (completion & feeling) - [ ] **Zeigarnik Effect** — Use progress indicators, clear signifiers of more content, and (honest) head-start progress to motivate completion. - [ ] **Goal-Gradient Effect** — Show proximity to the goal; people accelerate near the finish. Visible progress + a small head start works. - [ ] **Parkinson's Law** — Keep task duration at or under expectation — speed it up with autofill and smart defaults before it expands to fill the time. - [ ] **Peak-End Rule** — Invest in the emotional peak and the final moment (confirmations, success states, waits). Negatives are remembered more vividly — defuse them. - [ ] **Pareto Principle** — Are you investing effort in the ~20% of features/flows that drive ~80% of value? Prioritize there. - [ ] **Paradox of the Active User** — Users dive in without reading docs. Put guidance in-context (tooltips, inline hints) along whatever path they take. - [ ] **Cognitive Bias** — Watch for biases (e.g. confirmation bias) in both users and your own design/research decisions; design safeguards against them. ## Tensions & guardrails - Lenses conflict (Jakob's familiarity vs. a novel differentiator; Occam's minimalism vs. Tesler's irreducible complexity). Surface the tension and make a reasoned call. - The motivation lenses (Goal-Gradient, Zeigarnik, Peak-End, Cognitive Bias) can manipulate. Use them to help users finish *their* goals — a dark pattern is a critical finding, never a recommendation.