Compare the options
| Product | Who it suits | Trade-off |
|---|---|---|
 Modkat Litter Tray | Editorial pick for a cat that prefers an uncovered box: high sides, clip-on splash guard, walk-off platform. | Entry height is 6.5 in, while Cornell suggests low sides for kittens, seniors and cats with mobility problems. |
 Petmate Booda Clean Step | Editorial pick for an enclosed dome with a ramp and a replaceable charcoal filter. | Cornell's tips say most cats prefer uncovered boxes, so a dome only suits a cat that accepts one. |
 Modkat XL | Editorial pick for a covered box that lets you change how the cat enters. | The maker page lists two widths, so confirm the footprint before ordering. |
 Litter-Robot 4 | You are willing to use compatible clumping litter. | Routine drawer emptying and filter maintenance. Check the maker's litter rules before buying. |
 Purrify | Editorial pairing for plain litter in an open, dome or covered box; the 120g bag suits most homes. | Works with any litter, clumping included, but needs litter underneath. This page claims no Whisker certification. |
Modkat Litter Tray
Open, high-sided box measuring 20.3 by 14 by 9 inches, or 15.75 in tall with the guard on. It includes a removable Type G liner and a scoop. [3][5]
Petmate Booda Clean Step
Enclosed dome with a ramp, a carry handle and a replaceable charcoal filter. [1][5]
Modkat XL
Front, top and dual entry, a swivelling removable lid, reusable liners, a scoop and a holder with two odor filters. [2]
Litter-Robot 4
Litter-Robot 4 sifts clumps after use. Whisker describes a sealed waste drawer and a carbon filter for odor management, with optional OdorTrap Packs. Its FAQ accepts most clumping litter, and some beads or crystals small enough to pass the screen. [4][7][8]
Purrify
Fragrance-free activated carbon granules. Scatter two tablespoons over fresh litter, mix gently, and add more when the smell returns. [6]
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View on PurrifyOpen, covered and high-sided boxes
Cornell's Feline Health Center tips say most cats prefer uncovered boxes and suggest low-sided boxes for kittens, seniors and cats with mobility problems. Pick the Tray for an open box with high sides, the Booda if your cat accepts a cover, the XL if you want to adjust the entry.
[5][3][1][2]Self-cleaning boxes in plain terms
A self-cleaning box is an automatic box, so the maker's litter rules come with it. Whisker's Litter-Robot 4 guide calls for clumping litter. Our Litter-Robot litter page covers which litters to consider.
[4]Box size, material and cleaning access
The Modkat Tray measures 20.3 by 14 by 9 inches, and the XL page gives two widths, so confirm the exact size with the maker before ordering. Cleaning access differs: the Booda has a carry handle, the Tray a removable liner, the XL a swivelling lid and reusable liners, and the Litter-Robot 4 a drawer you empty.
[3][2][1][4]How litter choice fits the box
Cornell's tips say most cats prefer unscented, finer-textured litter, and the Litter-Robot 4 needs clumping litter. Purrify is fragrance-free and mixes into the litter itself, so it pairs with plain litter in the tray, dome or Modkat XL. The Purrify link is an affiliate link, so this site may earn a commission if you buy through it.
[4][5][6]Litter-Robot 4 for odor control
Whisker says the Litter-Robot 4 sifts clumps after use. Its FAQ describes a sealed waste drawer and a carbon filter for odor management, with optional OdorTrap Packs. The drawer still needs routine emptying and the filter needs maintenance. The guide calls for clumping litter, while the FAQ also allows some beads or crystals small enough to pass the screen.
[7][8][4]How we compare
These are desk comparisons. We read what the makers publish, set the products side by side and pick by fit. We have not tested the products ourselves, so the pages report no measured results, no lab figures and no numerical ratings. Every comparison lists its sources.
Sources checked
- Petmate, Booda Clean Step litter dome page Source read on 2026-10-23
- Modkat, Modkat XL litter box page Source read on 2026-10-23
- Modkat, Modkat Litter Tray page Source read on 2026-10-23
- Whisker, Litter-Robot 4 getting started guide (litter types) Source read on 2026-10-23
- Cornell Feline Health Center, house soiling tips (updated January 2015) Source read on 2026-10-23
- Purrify products Source read on 2026-10-23
- Whisker Litter-Robot 4 FAQ, checked 24 October 2026 Source read on 2026-10-24
- Whisker, Litter-Robot 4 product page Source read on 2026-10-24