Retractable belt barriers stretch across a space to temporarily restrict access, designate a route, or establish a queue for managing crowds. Mountable retractable belt barriers attach to walls, racks, or doorways to restrict access without occupying floor space with barrier posts. Retractable belt post barriers are freestanding, portable posts that have an internal cassette of rolled belt that pulls to extend and clips onto a nearby receiver post. Receiver posts for retractable belt barriers are freestanding, portable posts that have a slot for attaching a stretched belt from a nearby post. Retractable belt barrier systems consist of multiple interchangeable components of freestanding posts with retractable belts for assembling a barrier around a wide area without having to purchase separate components.