Five laws you can measure on any website
Fitts's Law
The time to hit a target depends on its distance and size. Make important buttons big and close.
DecisionHick's Law
Decision time grows with the number of choices. Fewer, clearer options lead to faster action.
MemoryMiller's Law
Short-term memory holds only a few chunks. Group information into small, meaningful sets.
ExpectationsJakob's Law
Users expect your site to work like the sites they already know. Follow conventions.
SpeedDoherty Threshold
Productivity rises when the system responds in under about 400 ms. Keep interactions instant.
PerceptionLaw of Proximity
Things placed close together look like one group. Use spacing to show what belongs together.
More laws and principles worth knowing
| Principle | What it says | How to apply it on a website |
|---|---|---|
| Tesler's Law | Every system has a certain amount of complexity that cannot be removed — only moved between the product and the user. | Absorb complexity in the product (smart defaults, autofill) instead of pushing it onto the visitor. |
| Law of Proximity | Items placed close together are perceived as belonging to the same group (Gestalt). | Keep labels next to their fields and related actions together; use space, not lines, to separate groups. |
| Aesthetic–Usability Effect | People perceive attractive designs as easier to use (Kurosu & Kashimura, 1995). | Polish matters, but don't let a beautiful design hide usability problems during testing. |
| Von Restorff Effect | When several similar items are shown, the one that differs is the one most likely remembered. | Make the primary call to action visually distinct — and only one per screen. |
| Serial Position Effect | People best remember the first and last items in a series. | Put the most important navigation items at the start and end of the menu. |
| Goal-Gradient Effect | Motivation increases as people get closer to a goal. | Show progress in sign-ups and checkouts, and give a head start where you honestly can. |
| Peak–End Rule | Experiences are judged mostly by their most intense moment and their end. | Design the success state and the thank-you page as carefully as the landing page. |
| Zeigarnik Effect | Unfinished tasks are remembered better than finished ones. | Onboarding checklists and saved progress bring people back to complete setup. |
| Postel's Law | Be liberal in what you accept and conservative in what you send. | Accept phone numbers, dates and URLs in any reasonable format and normalise them yourself. |
How to use the laws of UX without overdoing it
The laws describe average human behaviour measured in controlled experiments. Real pages mix many forces at once, so treat each law as a strong default and confirm important decisions with data:
- Prefer conventions over novelty unless you can prove the new pattern works better (Jakob's Law).
- Don't oversimplify: hiding options to satisfy Hick's Law can add clicks and confusion (Tesler's Law).
- Measure what can be measured — target sizes, contrast, number of choices, response time — and test the rest with users.
Lensux measures Fitts's Law on the rendered page (every tap target on desktop and mobile), counts navigation choices for Hick's Law, finds oversized groups for Miller's Law, checks the home link for Jakob's Law and times the server for the Doherty Threshold.
Frequently asked questions
What are the laws of UX?
They are a collection of principles from psychology and HCI research — such as Fitts's Law, Hick's Law, Miller's Law and Jakob's Law — that predict how people interact with interfaces. Designers use them to make decisions that are backed by evidence.
Who created the laws of UX?
Each law comes from a different researcher: Paul Fitts (1954), William Edmund Hick (1952), George A. Miller (1956), Jakob Nielsen (2000) and Walter Doherty with Ahrvind Thadani (1982), among others. Designer Jon Yablonski popularised them as a collection on lawsofux.com.
Are the laws of UX strict rules?
No. They describe tendencies measured in experiments. Use them as defaults and validate important decisions with analytics and user testing.