5 ways a litter box can clean itself

Rotating drum

21 models from 9 brands, ~$219–$899

The drum or globe is the design most people picture: the cat walks into an enclosed chamber, and after it leaves the whole thing turns so the litter passes through a screen and clumps fall into a drawer underneath. Drums contain scatter and smell well and publish the most safety detail. What they ask for is floor space, a step up to the entry, and trust that the sensors will see the cat, which is why the kitten threshold matters most here.

Open-top

8 models from 7 brands, ~$169–$640

Open-top boxes keep the cat out of any enclosure: the litter bowl tilts or rotates beneath an open rim, so there is no entry to squeeze through and nothing that closes over the cat. They suit large breeds and cats that refuse hooded boxes. They let more litter scatter, and several makers here rate them for the heaviest cats in the catalog.

Crystal tray

6 models from 2 brands, ~$100–$270

Crystal-tray boxes run on a disposable, pre-filled tray of silica crystals. A rake sweeps solids into a covered trap and the crystals absorb urine; when the tray is spent you lid it and throw it away. There is nothing to scoop, bag or empty, and the boxes are the cheapest to buy. The trays are the catch: a tray is roughly a month's supply for one cat, sold only by the maker.

Flushing

2 models from 1 brand, ~$469–$499

Flushing boxes are plumbed in: a cold-water line in, a drain hose out. After each visit they clean the bowl and send waste down the pipe, so nothing is ever emptied. They need a spot within reach of a drain and a steady supply of the maker's own cleaning cartridges and litter or granules.

Rake

2 models from 2 brands, ~$220–$280

A rake or comb crosses a fixed, open litter bed and pushes clumps into a bin at one end. The result looks and behaves most like an ordinary pan, low to the floor with no enclosure, but the bins are small and the litter surface is exposed.