The XR_EXT_local_floor extension.

The core OpenXR spec contains two world-locked reference space XrSpace types in XrReferenceSpaceType, REFERENCE_SPACE_TYPE_LOCAL and REFERENCE_SPACE_TYPE_STAGE with a design goal that LOCAL space gets the user positioned correctly in XZ space and STAGE gets the user positioned correctly in Y space.

As defined in the core OpenXR spec, LOCAL space is useful when an application needs to render seated-scale content that is not positioned relative to the physical floor and STAGE space is useful when an application needs to render standing-scale content that is relative to the physical floor.

The core OpenXR specification describes that standing-scale experiences are meant to use the STAGE reference space. However, using the STAGE forces the user to move to the stage space in order to operate their experience, rather than just standing locally where they are.