OpenXR

OpenXR is an open, royalty-free standard for access to virtual reality and augmented reality platforms and devices. It is developed by a working group managed by the Khronos Group consortium. OpenXR was announced by the Khronos Group on February 27, 2017 during GDC 2017. A provisional version of the standard was released on March 18, 2019 to enable developers and implementers to provide feedback on it. On July 29, 2019, OpenXR 1.0 was released to the public by Khronos Group at SIGGRAPH 2019.
Reviewers of the 0.90 provisional release considered that the aim of OpenXR was to "Solve AR/VR Fragmentation".
Architecture.
The standard provides an API aimed for application developers targeting virtual reality or augmented reality hardware. This enables developers to build applications that will work across a wide variety of devices.
The fundamental elements of this API are:
Implementations.
The Khronos Group maintains the list of OpenXR-conformant platforms and products.
Currently conformant OpenXR platforms are:
Preview and early development releases of OpenXR are available for the following platforms:
Game and Rendering Engine Support.
Support for OpenXR application development can be found in the following engines:
Announced upcoming support:
Roadmap.
After the release of OpenXR 1.0, progress will likely be driven through the development of extensions to the core API. This can be seen in the subsequent release of extensions for support of hand tracking and eye gaze tracking. 
As implementers and developers get more experience with the extensions, they could get integrated into the core OpenXR API in future releases.
Contributors.
The following companies are listed by Khronos as public supporters of OpenXR: