How to test your app with five people before launch

Five people from your app's audience, each left alone to complete a few real tasks, will uncover most of the big usability problems. You don't need a lab. You need well-written tasks, an installable build, and the patience not to help. Then you fix things and test again, with five more.

Why five, not fifty

The number comes from a classic article published by Nielsen Norman Group in 2000, based on studies across a range of projects. In short: the first person finds close to a third of the usability problems. The second finds some of the same ones and a few new ones. With each extra person you see more repeats and fewer new issues. After five people, the first study has found 85% of the problems on average.

The recommendation there is to skip the single 15-person test and run three small tests with five people each, fixing things in between. The second round checks whether your fixes worked and surfaces problems that were hiding behind the big ones.

One exception matters: the rule holds for people who use the app in similar ways. If you have two very different kinds of users, say customers booking an appointment and staff receiving it, test them separately, with 3–4 people from each group.

Preparation: tasks, not questions

Don't ask "What do you think of the app?" You'll get a polite answer that tells you nothing. Give concrete tasks, the way the person would face them in real life:

1. "Book an appointment for Thursday afternoon."
2. "Change the time of your appointment."
3. "Find out how long delivery takes to your area."
4. "Delete your account."

Four to six tasks are enough for a half-hour session. Write them on paper, without the words used on the app's buttons. If the task says "tap Book," you've tested reading, not the app.

Pick people who resemble your customers, not coworkers or friends who have already seen the screens.

Getting the app onto their phones

For a test you need a build people can install. Both stores have tools for that:

A TestFlight build stays active for 90 days after upload, which is plenty for a few rounds. For five people, Android internal testing and a TestFlight link on iPhone are all you need. If the app is still at the prototype stage, you can also test a clickable prototype before any code exists.

During the test

• One person at a time, on their own phone or a phone you've set up.
• Ask them to think out loud: what they're looking for, what they expect a button to do.
• Don't help. When they get stuck, ask "What would you do now if I weren't here?" and take notes.
• Note where they hesitate, where they tap the wrong thing, which words they don't understand.
• If you want to record the screen or their voice, ask for their consent first.

After the test: what to fix first

At the end, put all your notes on one list and sort them into three groups:

1. Blocks the task: the person couldn't finish. Fix these before any launch.
2. Slows them down: they made it, but hesitated or took a wrong turn. Fix these in this round if you can.
3. Annoys them: an odd label, a color, an icon. Note them for later.

A problem seen by three people out of five is no longer an opinion. Fix it, upload a new build and bring in five new people.

If you're just starting with an app idea, also read the smallest app worth launching and the sign-up screen, where most people drop off. What we do at each stage, from prototype to launch, is on our App Dev services page.