Welcome to the Godot OpenXR Vendors plugin documentation!
The Godot OpenXR Vendors plugin is a GDExtension for Godot 4, that adds support for OpenXR vendor extensions, which can't be made part of Godot itself, because they are too specific to a particular vendor.
As just a handful of examples, this plugin adds support for Meta's scene anchors and HTC's face tracking extension.
It also includes support for various Android OpenXR loaders. Until they can standardize on the Khronos loader, a number of vendors need to use a proprietary OpenXR loader on Android.