Recent technological advances enable seamlessly changing between different degrees of reality and virtuality using consumer hardware. This so-called cross-reality brings new chances to solve tasks that augmented and virtual reality alone were not fit for, but it also brings new challenges, for example when users need a mental representation of the content that is currently not visible and when choosing and executing transitions between realities. I propose to use context awareness to lower the mental load in such situations and to improve overall user-friendliness. My thesis begins with a literature research to gain an overview of the specific challenges and existing approaches in cross-reality context awareness. From the results, first, a taxonomy will be developed. There will also be a solution in the form of a framework supporting the inclusion of context awareness into cross-reality experiences. The taxonomy will additionally be the base for cross-reality building blocks that can be used in the framework. The results will be evaluated in developer and end-user studies to ensure that the framework is usable and solves the found challenges.