Some robot vacuums include a mopping capability to meet all your floor’s cleaning needs with one device. While this sounds like a great idea, in practice it often yields subpar results. The problem is the method these hybrid devices use for wet cleaning. Mopping robot vacuums include a flat, small-capacity water tank that you fill from your tap. A microfiber cloth is then attached to the bottom of the tank, and the tank is installed under the robot. As the robot rolls across the floor, it drags the dampened cloth over it. This usually removes surface grime and spills but leaves deeper dirt and stains behind. If you have a lot of hard flooring in your home, it's worth considering a dedicated robot mop. These appliances are better suited to wet cleaning, spraying water directly on the floor to soften gunk and stains, and applying some agitation via a scrubbing pad or brush. If you still want a vac/mop hybrid, look for one that has spinning brushes or pads as opposed to a cloth that attaches to the bottom of the appliance. A model with a docking station that can clean those brushes or pads and reservoirs for clean and dirty water are even better. Those models will, of course, cost quite a bit more.