Prototype

An early, rough version of a product built to test an idea before investing in the finished thing. A prototype can be clickable screens, a sample garment or a basic working model, and its only job is to answer a question quickly and cheaply.

A prototype lets you get honest feedback and fix problems while changes are still cheap. It saves you from building the wrong thing beautifully and then having to start again.

Before writing any code a founder makes a clickable prototype of the app in a design tool and watches five people try to use it, spotting confusing steps in an afternoon.