Title: Federated learning using mixture of experts. Abstract: Federated learning has received attention for its efficiency and privacy benefits,in settings where data is distributed among devices.   Although federated learning shows significant promise as a key approach when data cannot be shared or centralized, current incarnations show limited privacy properties and have short-comings  when  applied  to  common  real-world  scenarios.   One  such  scenario is heterogeneous data among devices, where data may come from different generating distributions. In this paper, we propose a federated learning framework using a mixture of experts to balance the specialist nature of a locally trained model with the generalist knowledge of a global model in a federated learning setting.  Our results show that the mixture of experts model is better suited as a personalized model for devices when data is heterogeneous, outperforming both global and lo-cal models.  Furthermore, our framework gives strict privacy guarantees, which allows clients to select parts of their data that may be excluded from the federation.   The evaluation shows that the proposed solution is robust to the setting where some users require a strict privacy setting and do not disclose their models to a central server at all, opting out from the federation partially or entirely.  The proposed framework is general enough to include any kind of machine learning models, and can even use combinations of different kinds.