This article describes the UniversAAL platform, an open platform intended to facilitate the development, distribution, and deployment of technological solutions for Ambient assisted living (AAL). The platform is intended to benefit end users (i.e., assisted persons, their families, and caregivers), authorities with responsibility for AAL, and organizations involved in the development and deployment of AAL services. It consists of an extensive set of resources (some are software and some are models/architectures) aimed at these different groups. The resources are classified into three main groups: runtime support, development support, and community support. The article presents the benefits that can be expected from the widespread adoption of the platform. The article also describes progress on prototype implementations of some of the software resources, and the results of initial evaluations of the platform. The work is partially based on results from earlier European Union-funded research projects in the area.