Current dark pattern research tells designers what not to do, but how do they know what to do? In contrast to prior approaches that focus on patterns to avoid and their underlying principles, we present a framework grounded in positive expected behavior against which deviations can be judged. To articulate this expected behavior, we use concepts—abstract units of functionality that compose applications. We define a design as dark when its concepts violate users’ expectations, and benefit the application provider at the user’s expense. Though user expectations can differ, users tend to develop common expectations as they encounter the same concepts across multiple applications, which we can record in a concept catalog as standard concepts. We evaluate our framework and concept catalog through three studies, illustrating their ability to describe existing dark patterns, evaluate nuanced designs, and document common application functionality.