Litter-Robot 4 Review: The Mature Choice Now That the Litter-Robot 5 Has Arrived

The Litter-Robot 4 is a globe on a pedestal. The upper sphere holds the litter and rotates to sift, the base holds the waste drawer, the electronics and the weight sensors. Nothing electrical sits inside the globe, which is the reason Whisker can state in the Litter-Robot 4 manual that there are no rakes or wires where the cat stands.

The published footprint is 22 by 27 inches, or 56 by 68.6 centimeters, and the unit stands 29.5 inches tall at 75 centimeters. Empty, it weighs 24 pounds, about 10.9 kilograms. Those numbers are worth measuring against a real corner before ordering, because the manual adds a rule that is easy to miss. The unit must not touch a wall on any side, since contact throws off the weight sensors that detect the cat. A box that fits the floor space may still not fit the clearance requirement.

Surface matters for the same reason. Whisker specifies a firm, level floor and sells a carpet tray for homes where that is not possible, stating that the weight readings are most accurate off carpet. The entryway is a circular opening measured at 15.75 by 15.75 inches, or 40 by 40 centimeters, and the step up from the floor to that opening is 30.5 centimeters. For an older cat or one with joint trouble, that climb is the single most important number in the table, and Whisker sells a ramp for it.

Build quality reads well in independent hands. Cats.com's testers, who have run the unit across several households, listed good build quality and an effective design among the things they liked, alongside the availability of published replacement parts and repair guides.

The globe rotates counterclockwise after the cat leaves. A flexible liner inside falls away from the wall as the globe turns upside down, clumps drop through a screen into the waste port, and the globe then rotates back so the clean litter spills into place. Before it settles, it rotates past the home position once to level the bed. That sequence is set out step by step in the manual, and it explains why there is no rake to jam.

The delay before a cycle starts is adjustable from 3 to 30 minutes, with 7 minutes as the figure Whisker uses in its own guidance for waste to clump. If the cat re-enters during the countdown, the sensors restart it.

On how well that works in practice, the most useful evidence comes from Cats.com's long-running test, whose testers used the box for months with clumping clay litter. They reported that the rotating sifting mechanism does not tend to jam the way rake-based boxes do, that cycles ran consistently whether triggered automatically, by the panel button or from the app, and that clumps separated without much residue or sticking.

The constraint is litter type. Whisker specifies clumping litter, or beads and crystals small enough to fall through the screen, and rules out strictly absorbent, non-clumping, loose-clumping, newspaper and wood pellet products. Lightweight corn and wheat litters may not pass the screen properly. Cats.com puts it more bluntly for one popular category, noting that tofu litter will not work. Anyone committed to a plant-based litter should treat that as disqualifying.

Waste falls into a drawer in the base that measures 5.5 by 13.5 by 9.25 inches, or 14 by 34.3 by 23.5 centimeters. Whisker does not publish a volume for it, so the manual instead gives a practical figure: the drawer takes a standard bin liner of 37 to 49 liters, and the company recommends changing it weekly for one cat and twice weekly for two.

Odor control rests on two things working together. The drawer seals, and a carbon filter sits above it, with optional scented packs available in place of the filter. The sealing is what does the work. Cats.com's testers reported that they did not notice litter box odor unless the drawer was open, and that smells were otherwise contained.

The drawer on the 4 is smaller than the one on the Litter-Robot 3, which sounds like a downgrade and mostly is not. The same testers found waste collected more evenly in it, dropping towards the center instead of piling against one side, so more of the volume gets used. They also noted the fullness sensor is more sensitive than the older model's, to the point that the tray filled right to the top before a notification appeared. If the app is your only prompt to empty it, you may be emptying a very full drawer.

One historical fault belongs here. Cats.com reports that the original fence attaching to the front of the unit allowed urine to leak through a gap between the globe and the base. Whisker released an improved fence and a bezel guard for owners who prefer not to use the fence, and corrected the design on the Litter-Robot 5. Anyone buying a used unit should check which fence came with it.

Whisker calls the detection system OmniSense, and it combines two different methods. Weight sensors in the base register a cat standing in the globe, and laser curtain sensors across the opening catch a cat that peeks in or steps in without putting enough weight down. Cats.com describes that pairing as the reason the 4 was the safest Litter-Robot to date, since the older model relied on weight alone.

If a curtain sensor triggers during a cycle, the globe stops, and the manual states it waits 15 seconds after the cat leaves before resuming. Two anti-pinch safety features and an overload detection system cover the case where the globe jams or meets resistance. These are documented behaviors with described light-bar signals, and the manual is specific enough that an owner can tell a safety stop from a fault.

The cat side has two hard limits. Automatic mode needs a cat of at least 3 pounds, about 1.36 kilograms, because the weight scale will not register anything lighter. Whisker's own answer for kittens below that is to run the box unplugged and power it on manually after use, which works but defeats the point of an automatic box. At the other end Whisker states there is no weight limit, and points to the 15.75 inch entryway and the 15 to 17 inch interior height as evidence that almost any domestic cat fits.

That claim deserves a caveat, and the independent evidence supplies it. The globe on the 4 is about an inch smaller inside than on the Litter-Robot 3, and Cats.com reports that some owners find the interior cramped for large cats and lists the smaller litter bed among the things it did not like. No weight limit is not the same as comfortable for a large cat, and a Maine Coon owner should treat the 90 day home trial as the actual test.

The Whisker app shows litter level, waste drawer level, per-cat weight from the SmartScale and a running activity log of cycles and visits. It needs iOS 13 or Android 8 as a minimum, and several people in a household can use the same account. For a multi-cat home the weight history is the feature with real value, because a cat quietly losing weight is something an owner rarely notices and a scale under the litter box records every few days without anyone remembering to do it.

The connectivity limit is the part to check before buying. Whisker states that the Litter-Robot 4 requires a 2.4 GHz network and does not support 5 GHz. Its support article on onboarding failures goes further, warning that mesh routers combining both bands can steer the unit onto the faster band after a successful setup, at which point it disconnects and will not come back. The documented workaround is a dedicated guest network on the older band, and the same article asks owners to confirm that ports 443 and 8443 are open. That is more network administration than a litter box should need, and on a modern mesh system it is a realistic source of frustration.

A disconnected box still cleans. The cycle logic runs on the unit, and the panel buttons work regardless. What stops is the remote view, the alerts and the weight history, which is the same pattern across this category and one we have looked at in detail in what actually keeps working when a smart feeder or litter box goes offline.

Running costs are modest and mostly optional. Carbon filters and drawer liners are consumables, though the manual permits any 37 to 49 liter bin liner in place of branded ones. The warranty is WhiskerCare for one year, with a three year plan sold separately. The direction of travel is worth watching: Whisker's newest hardware ties some insight features to a paid Whisker plus membership, while the Litter-Robot 4's app functions do not require one today. Since the box sits on your home network and logs your cat's habits, it is also a reasonable candidate for our checklist for securing a smart pet device.

Whisker now sells four Litter-Robots: the 5 Pro, the 5, the 4 and the smaller EVO. The Litter-Robot 5 is built on the same footprint as the 4 and adds WasteID, which Whisker says distinguishes solid from liquid waste, an updated scale, and support for up to five cats between 3 and 30 pounds. The 4 is rated for up to four cats. Whisker dropped the price of the 4 when the 5 launched, and the gap between them is the whole question.

Cats.com's 2026 roundup of 38 models ranks the Litter-Robot 5 Pro first and the Litter-Robot 4 second, describing the 4 as having years of software patches behind it and calling it one of the most reliable automatic litter boxes on the market. That ordering is the useful signal. The newer model is better, the older one is the safer bet on maturity.

That maturity is not a slogan. Cats.com reports that sensor malfunctions were fairly common in the months after the 4 launched and have since been addressed through firmware and app updates. A buyer today gets the version that came out of four years of that work, while the 5 is at the start of its own cycle. The 5 Pro is also the first model designed around Whisker's paid membership, which is a different ownership proposition.

Outside Whisker's range, the honest comparison set for a buyer who balks at the price is narrower than the search results suggest. Cats.com's budget pick in the same roundup is the PetSafe ScoopFree SmartSpin, and the highest-ranking non-Whisker smart box in Amazon's self-cleaning category on the day this review was researched was the PETKIT PuraMax 2. Neither has been assessed on this site yet, so treat those as leads for now.