A virtual space configuration system of an artificial reality system can detect a user posture and provide various corresponding customizations of the system's virtual space. The virtual space configuration system can, when a user is in a seated posture, provide for seated virtual space customizations. In various implementations, these customizations can include allowing adjustment of a floor height; setting a flag that can be surfaced to applications to adjust the applications' mechanics for seated users; customizing display of virtual space boundaries when in seated mode to be less intrusive; providing options to detect when a user leaves seated mode and trigger corresponding actions; provide a passthrough workspace area allowing a user to interact with certain real-world objects naturally without having to remove a virtual reality headset; or automatically determining virtual space dimensions for seated users.