The use of preliminary models and mockups for evaluative purposes.

The use of prototyping in interior design is similar to how it is used in the other physical design disciplines, such as architecture and industrial engineering. Prototyping takes many forms and is used at various stages of the design process to test out concepts, ideas, and details. Prototypes can be quickly tested in sketches and three-dimensional representations. They are used as a tool to boost creativity and communicate a design idea.

Full-scale mock-ups, 3D printed elements, and larger models are prototyped later in the design process once initial testing has occurred, and are used to test custom elements such as custom wall finishes, cabinet joinery, upholstery, or unique furniture elements. Prototypes can confirm concepts at that key moment prior to full fabrication. Prototyping is iterative by nature; the design evolves by testing it against function, usability, or effect. Mock-ups at this phase are prepared by a fabricator or contractor for designer and client approval.