In paper prototyping, the user interface of a system is reproduced from paper. A respondent performs predefined tasks with the prototype, while the performer adjusts the paper interface in real time to simulate the behavior of the system. By testing the prototype, an impression of the interface design can be gained quickly. Problems can easily be found and improvements can be derived.
Tests on paper prototypes can be used to detect usability problems by executing tasks or to compare several design alternatives. The complexity of paper prototypes is usually still relatively low. However, the tests are low cost and can be carried out in an agile manner.