This tutorial introduces the concept of playtesting - a central component of software development processes in the game industry - which is the process through which players inform the ongoing evolution of a game’s design. The importance of playtesting is derived from the fact that in the game industry, the quality of the software produced is measured in terms of the user’s subjective experience of it. In the tutorial the participants explore the benefits, pitfalls and relevance of playtesting for their business, be it a game company or any other software development operation.