UX Glossary · P
Prototype
A working approximation built to answer a question, at the lowest fidelity that answers it.
A prototype is something that behaves enough to be tried. Unlike a mockup, it responds. Unlike the product, it only has to work for the path being examined.
Fidelity is a decision, not a stage
The right fidelity is the lowest one that answers the question.
Paper answers whether a concept and its structure make sense, in an afternoon. Clickable wireframes answer whether a flow holds together. High-fidelity interactive prototypes answer questions about visual hierarchy, microcopy and timing, and are what most people mean by the word today. Coded prototypes answer questions about real data, performance and interactions a design tool cannot simulate.
Building higher fidelity than the question requires wastes time and, worse, changes the feedback: people review the visual design of a polished prototype instead of the concept.
Why it is the cheapest insurance available
A prototype is the last point at which being wrong is inexpensive. A concept invalidated in a week costs a week; the same finding after a quarter of engineering costs a quarter.
The trap
Prototypes that become the product. Code written to answer a question was not written to be maintained, and “we will rewrite it properly later” is one of the more reliably broken promises in software.
In practice
Write the question on the prototype. If nobody can state what it is testing, it is a demo.