ApertusVR is a free, open-source, cross-platform, distributive, multi-user, IoT supported XR (AR, VR, MR) engine (programming library). ApertusVR offers a brand new “no vendor lock-in" approach for virtual and augmented reality on different operating systems and on different virtual, augmented and mixed reality hardware. The cross-platform Apertus engine eliminates industry fragmentation by enabling applications to be written once to run on any XR system and to access different XR devices.