A prototype is a preliminary visual mockup of an app designed to look and feel like the real thing. They’re much quicker to make, and although they don’t include all the expected features, they allow you to spot mistakes before you build the real thing.

A prototype can be as simple as sketches on paper (low fidelity) or as intricate as a clickable, digital model that works on your phone (high fidelity). It can illustrate one key screen, a complex flow, or all the key features of an app. And it can be created with or without code.

The goal of a prototype is to represent and demonstrate an app's fundamental design and function without being fully functional. As such, it’s typically used in conjunction with user interviews to get feedback from real users.

A user’s reactions and responses while using a prototype will help validate if your app is on the right track; from either an idea or a design standpoint.

For example, Airbnb might've made a prototype of what the process would look like to book a stay on their platform and used it in user interviews to elicit a reaction from potential users.