Comparison searches for these models usually want a winner. A spec sheet cannot give you one, because the products solve the scooping problem in three different ways and make different demands on your household. What a spec sheet can do is remove two of the three quickly. If you will not switch to crystal litter, ScoopFree is out. If a cat is over 25 lb, Litter-Robot 4 is out by Whisker’s own range, and the open-top M1 Plus is the one with a documented range that still covers it. What follows is each maker’s documented position, side by side, with unconfirmed items marked. BowlScout does not run hands-on tests; see the methodology page.
The Three Mechanisms in One Paragraph Each
Litter-Robot 4 is a rotating globe. After a delay you set between 3 and 30 minutes, the globe turns, a screen sifts clumps into a sealed, carbon-filtered drawer in the base, and the clean litter returns. Whisker’s sensors — lasers, weight and anti-obstruction detection — stop the cycle when a cat approaches, and SmartScale uses the weight reading to tell cats apart in the Whisker app.
PetSafe ScoopFree Crystal Smart (PAL00-16807, uncovered; PAL00-16808, front-entry) is a flat tray. According to PetSafe’s support guide, a sensor tells the rake to start a scoop cycle 20 minutes after the cat uses the box; the rake pushes solids into a covered waste bin at the end of the disposable tray. Crystals absorb liquid rather than clumping. When the tray is spent, the whole tray is thrown away and replaced — “just once a month”, in PetSafe’s words, without a cat count attached.
Neakasa M1 Plus is an open-top basin with no enclosure. The basin tilts and sifts litter through a screen into an 11.23 L waste bin; cats step in over a 13.86″ entry height. Neakasa publishes a weight range of 2.2 lb to around 33 lb, a Kitten Mode that prevents automatic cleaning for cats under 2.2 lb, and infrared sensors for detection (its page now describes the “M1 Plus” revision with six sets).
Side-by-Side Specifications
| Specification | Whisker Litter-Robot 4 | PetSafe ScoopFree Crystal Smart | Neakasa M1 Plus |
|---|---|---|---|
| Mechanism | Rotating globe, sifting screen, drawer | Raking tray, covered waste bin | Open-top tilting basin, sifting screen, waste bin |
| Litter | Clumping clay recommended; non-clumping, newspaper, wood pellets excluded | “Designed for use with crystal litter only”; disposable pre-filled trays | Clumping or scoopable litter; “fast-clumping, granular litter such as bentonite” recommended; absorbent, non-clumping, loosely clumping, newspaper and wood pellets excluded; filter sifts up to 3 mm × 10 mm |
| Cat weight range | 3–25 lb | Not published | 2.2 lb to around 33 lb; Kitten Mode below 2.2 lb |
| Stated cat count | Up to 4 cats | “Single or multi-cat households” | Multi-cat, no number |
| Size | Footprint 22″ × 27″; 29.5″ tall; entry 15.75″ × 15.75″; interior height 16.5″ | 27.6″ × 19.1″ × 6.2″ uncovered; 15.6″ tall with front-entry hood | Entry height 13.86″; overall footprint not published on the US page |
| Empty weight | 24 lb | Not stated | 22.81 lb (10.35 kg) |
| Waste capacity | Drawer: “up to 8 days” in a 1-cat household | Tray: change “just once a month” (no cat count given) | 11.23 L bin: “up to 14 days”; litter capacity 7.17 L |
| Cycle timing | 3 to 30 minutes after use, adjustable | Scoop cycle 20 minutes after use (support guide) | Not published as a delay figure |
| Safety sensors | Lasers, weight sensors, anti-obstruction | Rake sensor detects use | Infrared sensors (six sets in the M1 Plus revision) |
| Noise claim | “QuietSift” (no dB figure) | None published | ≤ 50 dB (manufacturer figure) |
| App | Whisker app; weight-based cat ID; 7-day history free, longer with Whisker+ | My PetSafe app; activity log; tray-change alerts; LCD health counter on the unit | Android and iOS app |
| Wi-Fi | 2.4 GHz only; IPv4 or IPv6 | Wi-Fi (band not stated on the page) | Not stated on the page |
| Power | 15 V DC adapter | Plug-in | Not stated on the page |
| Odor control | Sealed, carbon-filtered waste drawer | Crystal litter; “5X better odor control” is PetSafe’s claim | Sealed bin (Neakasa’s “odor-lock” description) |
| Warranty, trial, returns | 1-year warranty; 90-day in-home trial; 3-year plan optional | 45-day return window stated on the page; warranty not stated | 2-year warranty; 30-day return |
Sources: Litter-Robot 4 on litter-robot.com and whisker.com; ScoopFree Crystal Smart PAL00-16807 and the ScoopFree support guide; Neakasa M1 Plus.
Where Each One Stands on Paper
Litter-Robot 4: the most complete spec sheet
Whisker publishes more numbers than the other two: a weight range, a cat count, an entry size, an interior height, a drawer rating in days, a delay range, a Wi-Fi band and a trial period. That does not make it the better machine; it makes it the easiest to rule in or out. The limits are real, too: a 25 lb ceiling, 2.4 GHz-only networking, and a recommendation for standard-weight clumping clay rather than lightweight litters.
ScoopFree Crystal Smart: the lowest profile and the only non-clumping option
At 6.2″ tall uncovered, ScoopFree fits under furniture that no globe or basin will. It is also the only one of the three where you never touch litter — the tray goes out whole. The trade-offs are a continuing tray purchase, a litter type many cats have never used, and the thinnest documentation: PetSafe publishes no cat weight range and no cat count, and its product FAQ merely asks whether a kitten can use it. Its app features are also narrower: an activity log and tray alerts rather than per-cat identification.
Neakasa M1 Plus: the widest weight range and no enclosure
Neakasa’s 2.2 lb to around 33 lb is the widest documented range in this comparison, its 11.23 L bin carries the longest one-cat rating of the three (up to 14 days), and the open top removes the entry hole that some cats refuse. The costs are floor space and a tall step: the basin has a 13.86″ entry height, and Neakasa does not publish the overall footprint on its US page, so measure against the listing’s dimensions. The page also now describes the “M1 Plus” revision, so confirm which revision you are buying.
How This Changes With Litter-Robot 5
Whisker’s newer Litter-Robot 5 shares Litter-Robot 4’s footprint and entry size but lifts the weight ceiling to 30 lb and the cat count to 5, adds WasteID (which Whisker says distinguishes urine from feces to time the cycle), a colour LCD, 17.5″ of headroom and a drawer Whisker rates at every 10 days for one cat. If the 25 lb ceiling or the 8-day drawer is what stops you on Litter-Robot 4, the newer model is the comparison to make before leaving the Whisker range. Our multiple-cats guide covers the drawer arithmetic.
The Cards
Neakasa references on this page now cover M1 Plus. Its exact Amazon offer is the Entrance Litter Guard bundle. Litter-Robot 5 remains an editorial comparison with manufacturer sources; no exact Amazon listing was established, so it has no purchase card. Litter-Robot 4 remains a separate option within its own 3–25 lb range and up-to-four-cat limit.
Neakasa M1 Plus — Entrance Litter Guard bundle
Open-top self-cleaning litter box. Neakasa states a 2.2 lb to around 33 lb range, a 13.86-inch entry and an 11.23 L waste bin. The Plus revision uses six infrared sensor arrays. This Amazon offer includes the entrance litter guard; confirm the selected bundle and accessories.
Whisker Litter-Robot 4
Best for: Homes with up to four cats in the 3–25 lb range that want weight-based cat identification without cameras.
- Whisker lists it for cats 3–25 lb and “up to 4 cats”
- entryway 15.75″ × 15.75″; interior height 16.5″; footprint 22″ × 27″; 29.5″ tall
- cleaning cycle starts 3 to 30 minutes after use; sealed, carbon-filtered waste drawer; 2.4 GHz Wi-Fi only
PetSafe ScoopFree Crystal Smart
Best for: A raking tray design for households already using crystal litter and disposable trays.
- “Designed for use with crystal litter only”; disposable pre-filled trays that PetSafe says to change “just once a month”
- uncovered unit 27.6″ × 19.1″ × 6.2″ (front-entry version PAL00-16808 is 15.6″ tall); plug-in power
- rake scoops 20 minutes after the cat uses the box (PetSafe support guide); My PetSafe app activity log and tray alerts; LCD health counter
To test your cats’ weights, your litter and your floor space against all three at once, use the litter box fit check.
Running Costs Are Different in Kind
Litter-Robot 4 and the M1 Plus consume ordinary clumping litter plus drawer liners or bags; Whisker also sells carbon filters and odor packs for the drawer. ScoopFree consumes pre-filled crystal trays. We do not publish prices, but the structure matters: a tray system ties you to one consumable from one maker, while a globe or basin takes any approved clumping litter from any brand. Whisker also sells optional items — a 3-year extended warranty plan and a Whisker+ membership for longer app history. None of these is required for the box to cycle.
Quick Checklist Before You Buy
- You have decided between clumping litter (Litter-Robot 4, Neakasa M1 Plus) and crystal trays (ScoopFree)
- Every cat sits inside the documented range: 3–25 lb for Litter-Robot 4; 2.2 lb to around 33 lb for the M1 Plus; no range is published for ScoopFree, so ask PetSafe
- The spot fits the height with the drawer or tray pulled out: about 29.5″ for the globe, 6.2″ or 15.6″ for ScoopFree, and the M1 Plus’s footprint from the listing
- Your router offers a 2.4 GHz network (required by Whisker; confirm for the others)
- You know the one-cat capacity rating and have divided it by your number of cats
- You have read the trial, return and warranty terms for the model you choose
Frequently Asked Questions
Which of the three is quietest?
Only Neakasa publishes a figure (50 dB or less). Whisker describes QuietSift without a number and PetSafe publishes none. We have not measured any of them, so there is no documented answer beyond Neakasa’s own claim.
Can ScoopFree use clumping litter?
PetSafe says the unit is designed for crystal litter only, and its support guide says not to use another type because it will not scoop properly.
Does Litter-Robot 4 work with lightweight litter?
Whisker recommends high-quality, standard-weight clay-based clumping litter and lists non-clumping, newspaper-based and wood-pellet litters as incompatible. Lightweight clumping litter is not on either list; follow Whisker’s recommendation.
Is an open-top box safe with a kitten in the house?
Neakasa publishes a Kitten Mode for cats under 2.2 lb that prevents automatic cleaning, so the box behaves like a static tray until the kitten grows. Whisker’s floor is 3 lb in automatic mode. Below those weights, the makers are telling you to run the device manually.