Usability testing

Usability testing, one of the core methods of UX design, is about watching behaviour, not collecting opinions. Asking someone whether they like a design tells you little; asking them to book an appointment and watching them search for the button tells you a great deal. The aim is to find problems, so a test that turns up nothing has usually been made too easy.

It differs from A/B testing, which compares two live versions using large numbers of visitors to see which performs better. Usability testing uses a handful of people to find out why something is hard. A/B testing tells you what happened; usability testing helps explain why.

How it works

A facilitator gives each participant a few realistic tasks, such as finding the price of a service and requesting a quote, and asks them to think aloud as they go. Sessions can be in person or remote, moderated by a researcher or unmoderated through a testing platform that records the screen and voice. Observers note where people get stuck, what they misread and what they expected to happen.

Testing can happen at any stage, from a paper sketch or prototype to the live site. Nielsen Norman Group's long-standing advice is that small rounds of around five participants reveal most of the major problems, with the fixes checked in another round.

Writing the tasks is a skill of its own. A good task describes a goal in the customer's words rather than the site's labels: you want a cake for Saturday and need to know whether it can be delivered, rather than use the delivery checker. Using the site's own button names gives the answer away. After each session, note each problem, how many people hit it and how badly, then fix the most serious first and test again.

Example

A family bakery tests its new online ordering site with five regular customers. Three of them cannot find where to choose a collection time, because it sits in a collapsed panel below the basket, and two think the delivery fee is a deposit. Moving the time picker into the main checkout step and relabelling the fee takes an afternoon, and the next round of testers completes an order without help.

The bakery recruits testers by asking regular customers in the shop, with a free coffee as thanks, and runs the sessions on the testers' own phones so the test reflects real devices and real connections. The owner watches silently and resists the urge to explain. Afterwards the problems are listed by severity: anything that stops an order is fixed first, while a confusing but harmless label waits for the next round.

Why it matters for your business

Usability testing finds the problems that make people abandon forms and bookings before you spend money sending traffic to them. It is one of the cheapest research methods: a few sessions with the right people can save weeks of building the wrong thing. It does not need a lab; recruiting a handful of real customers and watching them use the site over a video call is often enough. The main risk is testing with the wrong people, such as colleagues who already know how the site works.

Common mistakes

• Testing with staff or friends who already know the business and its jargon.
• Asking leading questions or helping participants as soon as they get stuck.
• Testing only once, just before launch, when changes are most expensive.
• Collecting opinions about colours and layout instead of observing whether tasks get done.

Questions people ask

How many people do you need for usability testing?

For qualitative tests aimed at finding problems, small rounds of around five participants are a widely used guideline, because the same major issues tend to appear again and again. Run several small rounds with fixes in between rather than one large study. If you need statistics, such as comparing success rates, you need many more participants.

How much does usability testing cost?

Costs vary widely. Informal tests with a few customers over a video call can cost little beyond time and a small thank-you gift. Professional studies with recruitment, a researcher and a report cost considerably more. Remote testing platforms sit in between and usually charge by subscription or per session.

What is the difference between usability testing and user research?

User research is the broad discipline of learning about users through interviews, surveys, analytics, field visits and more. Usability testing is one specific research method focused on whether people can complete tasks with a particular design. Research helps decide what to build; usability testing checks whether what you built can be used.