Introducing the gmix open source framework for mix implementations. In this paper we introduce the open source software framework gMix which aims to simplify the implementation and evaluation of mix-based systems. gMix is targeted at researchers who want to evaluate new ideas and developers interested in building practical mix systems. The framework consists of a generic architecture structured in logical layers with a clear separation of concerns. Implementations of mix variants and supportive components are organized as plug-ins that can easily be exchanged and extended. We provide reference implementations for several well-known mix concepts.