UX laws are not arbitrary rules — they are observations about how human perception, memory, and motor control actually work, distilled into design heuristics. Most of the ones below were popularised by Jon Yablonski’s Laws of UX project, which collected decades of psychology and human-factors research into a designer-friendly toolkit. Here are the ten worth memorising, each with a definition you can trust and an example you can use tomorrow.
Hick’s Law
Hick’s Law states that the time it takes to make a decision increases logarithmically with the number and complexity of the choices available. More options means more cognitive load and slower, more error-prone decisions. It is named after psychologists William Edmund Hick and Ray Hyman.
In practice this is why a checkout flow with one clear “Pay now” button converts better than a screen offering six payment methods, a coupon field, a newsletter toggle, and three upsells all at once. Streaming services hide their full catalogue behind a handful of curated rows for the same reason.
“Simplicity is about subtracting the obvious and adding the meaningful.” — John Maeda
Apply it: Break long option lists into progressive steps or sensible defaults so users face only a few choices at any one moment.
Fitts’s Law
Fitts’s Law predicts that the time to acquire a target is a function of the distance to the target and its size. Bigger, closer targets are faster and easier to hit; small, faraway ones cause slips and frustration. It comes from Paul Fitts’s 1954 study of human motor movement.
This is why primary buttons should be large and placed where the cursor or thumb already is, and why tiny “x” close icons in the far corner are a usability tax. On mobile, it justifies the comfortable 44–48px minimum touch target and bottom-anchored navigation within thumb reach.
Apply it: Make the most important action the biggest and nearest target, and never shrink destructive or frequent controls to save space.
Jakob’s Law
Jakob’s Law, coined by Jakob Nielsen, says users spend most of their time on other sites, so they prefer your site to work the same way as all the others they already know. Meeting established conventions lets people transfer existing mental models instead of relearning.
A shopping cart icon in the top right, a logo that links home, an underlined link — these conventions feel invisible because they match expectation. Reinventing them, like putting navigation in an unfamiliar place to look “innovative,” forces relearning and increases bounce.
Apply it: Follow platform and category conventions by default; only break a convention when you have evidence the new pattern is meaningfully better.
Miller’s Law
Miller’s Law is the observation that the average person can hold about seven (plus or minus two) items in their working memory at once. It originates from George Miller’s 1956 paper, though it is often over-applied — the real lesson is that working memory is limited, not that menus must have exactly seven items.
The useful design takeaway is chunking: phone numbers, card numbers, and IDs are grouped (e.g. 4242 4242 4242 4242) so each chunk fits comfortably in memory. Long forms and navigation benefit from being grouped into labelled sections rather than presented as one undifferentiated list.
Apply it: Chunk dense information into small, meaningful groups instead of expecting users to retain a long flat sequence.
Tesler’s Law
Tesler’s Law, also called the Law of Conservation of Complexity, states that for any system there is an irreducible amount of complexity that cannot be removed — it can only be shifted between the system and the user. Larry Tesler argued designers and engineers should absorb that complexity rather than push it onto people.
Email is the classic example: parsing “you@example.com” into a valid address is genuinely complex, but a good client handles it silently rather than forcing the user to specify the protocol. When you add a smart default, an autocomplete, or server-side formatting, you are taking complexity off the user’s plate and onto the product’s.
Apply it: Decide deliberately who bears each piece of unavoidable complexity, and default to the product carrying it, not the user.
Postel’s Law
Postel’s Law, the robustness principle from networking pioneer Jon Postel, says: “Be conservative in what you do, be liberal in what you accept from others.” Applied to interfaces, it means be tolerant of varied, messy user input while producing clear, consistent output.
A phone field that accepts “(555) 123-4567”, “555.123.4567”, and “5551234567” and normalises them itself follows this law. So does a search box that forgives typos or accepts both “USA” and “United States.” The system flexes so the human does not have to.
Apply it: Accept input in whatever reasonable format users naturally provide, then clean and standardise it behind the scenes.
Peak-End Rule
The Peak-End Rule, from Nobel laureate Daniel Kahneman’s research, says people judge an experience largely by how they felt at its most intense moment (the peak) and at its end, rather than by the average of every moment. Memory is selective and weighted toward those two points.
This is why a delightful order-confirmation screen or a thoughtful, fast checkout finish can redeem an otherwise ordinary flow, and why a clumsy error at the very end can poison the whole memory. A well-designed empty state or a celebratory success animation deliberately engineers a positive peak and end.
Apply it: Invest extra polish in the emotional high point and the final moment of a flow — they disproportionately shape how the whole thing is remembered.
Doherty Threshold
The Doherty Threshold holds that productivity soars when a system and its user interact at a pace (response under about 400 milliseconds) that neither has to wait for the other. Below that threshold the interaction feels conversational; above it, attention drifts and frustration grows. It comes from a 1982 IBM study by Walter Doherty and Ahrvind Thadani.
When real work cannot finish in 400ms, perceived performance still matters: skeleton screens, optimistic UI that updates instantly before the server confirms, and progress indicators keep the experience feeling responsive. A “like” that animates immediately, syncing in the background, respects this threshold.
Apply it: Aim for sub-400ms feedback, and where you can’t deliver it, fake responsiveness with optimistic updates and meaningful loading states.
Aesthetic-Usability Effect
The Aesthetic-Usability Effect describes how users perceive more attractive designs as easier to use, and are more tolerant of minor usability problems when a product looks good. It was documented in research by Masaaki Kurosu and Kaori Kashimura and later studied at the Nielsen Norman Group.
A visually polished onboarding screen earns goodwill that buys patience for small friction; a clean, well-spaced dashboard feels more capable even before the user tries anything. The caution is that beauty can also mask real problems in testing, so it should never replace usability work.
Apply it: Treat visual craft as a usability lever, but keep testing for real issues that good looks might be hiding.
Law of Proximity
The Law of Proximity is a Gestalt principle stating that objects placed close together are perceived as related or belonging to the same group, while space separates them into distinct groups. Proximity often overrides other cues like colour or shape in signalling relationships.
This is why a form label sits tight against its input, why a price hugs its product card, and why generous whitespace between sections tells the eye “this is a new topic.” Get spacing wrong — a label floating equidistant between two fields — and users genuinely misread which control it belongs to.
Apply it: Use spacing, not boxes or lines, as your first tool for grouping related elements and separating unrelated ones.
The takeaway
These ten laws are lenses, not commandments. Hick’s and Miller’s protect attention and memory; Fitts’s and the Doherty Threshold respect the body and the clock; Jakob’s, Postel’s, and Tesler’s keep you humble about how much users should have to learn or do; the Peak-End Rule and the Aesthetic-Usability Effect remind you that feeling is part of usability; and the Law of Proximity grounds it all in how perception actually organises a screen. Internalise the why behind each one, test against real users, and you’ll reach for the right principle instinctively instead of memorising a checklist.
