Litter-Robot 3 Vs. 4: The Big Differences, Based On Cat Testing

Since the first Litter-Robot self-cleaning litter box launched in 2000, the company has released numerous models that improve on the original’s design. The brand’s current flagship model is the Litter-Robot 4, while the Litter-Robot 3 Connect (released in 2017) remains an incredibly popular bestseller. We’re going to break down the similarities and differences when comparing the Litter-Robot 3 vs. 4. Both are Wi-Fi–enabled and have advanced features that detect when your cat is using the bathroom and when the waste drawer needs to be emptied, for example.

I live in a multi-cat household, and my three cats use both models regularly. While the Litter-Robot 4 and 3 Connect operate similarly, they have some notable discrepancies between their advanced safety features, sifting systems and odor control. To help you decide which automatic self‑cleaning litter box is a better fit for you and your cats, I break down the biggest differences between the Litter-Robot Connect 3 versus the 4 in this guide. But before I jump into the specifics, here’s a general overview of each of the automatic litter boxes.

There are two available versions of the Litter-Robot 3, and the Connect is the Wi-Fi–enabled model. The litter box connects to the companion app (called the Whisker app). Its best features include an effective safety system, reliable operation and waste drawer alerts. Note that when compared to the newer 4 model, it’s louder, has a smaller waste drawer and doesn’t control odor as well as the Litter-Robot 4. But the 3 Connect still has a lot to offer. It also costs $150 less than the 4 model, making it a good option for those who want the convenience of a self-cleaning litter box for less. Just note that cats must be at least 5 pounds to use this model, which comes in two colors: Grey and Beige.

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The Litter-Robot 4 is the brand’s newest model. Designed with multi-cat households in mind, the Wi-Fi–enabled litter box can accommodate up to four cats, thanks to a larger waste drawer and real-time monitoring of waste and cat litter levels. What’s more, it has sensors that make it safe for felines as small as 3 pounds. Some other standout features of the Litter-Robot 4 vs. 3 Connect include a wider entryway and better, more advanced odor control.

Whisker, Litter-Robot’s parent company, calls the model the “smartest, quietest self-cleaning litter box for cats,” and I have to agree. After testing several automatic litter boxes, including the Litter-Robot 3 Connect, I named the Litter-Robot 4 the best self-cleaning litter box overall. It comes in two basic colors, but you can upgrade the look with a colored bezel for an additional $50; colors range from a solid Lilac to a multi-hued Marble (pictured above).

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Overview Of Differences Between Litter-Robot Models

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Litter-Robot 3 Connect Vs. 4: In-Depth Comparison

Now that you have a general overview of each of the models, here’s how they compare in terms of setup, design, odor control, sensors, noise, deep cleaning and price.

Setup

Setup for both models is a cinch. They come fully assembled, so you just have to take them out of the box and plug them in. The biggest difference between them is how you connect (and reconnect) them to the Whisker app. To sync the robots with the app, you scan a QR code that’s on the machine. The Litter-Robot 3 Connect has the code in the back of the machine at the base. The Litter-Robot 4’s code, on the other hand, is more conveniently positioned under the waste drawer.

While this isn’t a big deal for the initial setup, the positioning of the QR code makes a difference if the Litter-Robot disconnects from the app and needs to be reconnected. When I need to reconnect the Litter-Robot 3 Connect, I have to take it out of the credenza it’s in and spin it around to find the QR code. With the Litter-Robot 4, I can just pull the waste drawer out and it’s right there—no need to fuss with the positioning. I also noticed the app now walks you through an optional firmware check that keeps everything current.

Design

The design is the biggest difference between the Litter-Robot 3 Connect and 4—and it’s not just about the looks. The construction also factors into odor control and how many cats the Litter-Robot can accommodate.

Let’s start with size. The Litter-Robot 4 is narrower than the Litter-Robot 3 Connect. While they have the same height (29.5 inches) and depth (27 inches), the Litter-Robot 4 measures 22 inches wide, compared with the 24.3-inch width of the Litter-Robot 3 Connect. At the end of the day, though, both of these Litter-Robots are big. Neither one of them is going to blend in seamlessly with its surroundings, so you have to be willing to sacrifice some space regardless of which model you pick.

That said, the Litter-Robot 4 has some design upgrades that can benefit your cat. For starters, the entryway is much wider: 15.8 inches compared with the Litter-Robot 3 Connect’s 10.3 inches. While my cats never seem bothered by the smaller opening of the latter, they definitely stick out of it more when they’re doing their business; they just seem more comfortable in the Litter-Robot 4. The step into the entryway is also closer to the ground on the newer model, so it can be a better option for smaller cats or senior cats with mobility issues. (Whisker does sell ramps to make the taller step on the Litter-Robot 3 Connect more manageable, but with the Litter-Robot 4, you don’t need it.) New buyers can also snag the Kickstart Kit, which bundles liners, carbon filters and odor-eliminators. Since the unit will likely be visible in your home due to its size, we like that the Litter-Robot 4 bezel now comes in eight swap‑in colors for quick style points.

Another notable difference is the waste drawer. The Litter-Robot 4’s drawer has an overall smaller footprint, though the area that collects waste is larger. This means you don’t have to change the trash bag as often. The Litter-Robot 4’s drawer also has a more rectangular shape, so waste spreads out more evenly. With the Litter-Robot 3 Connect, I often notice that clumps pile up in the center of the drawer, sending false signals to the sensors that the waste drawer is full. That doesn’t happen with the Litter-Robot 4. Additionally, the trash bag fully covers the waste drawer in the Litter-Robot 4. The Litter-Robot 3 Connect has clips inside the waste drawer to keep the trash bag in place, but if it’s not secured properly, it can cave in, creating a pretty annoying mess.

Odor Control

This ties into design, but it’s worth calling out odor control separately since it’s one of the most vital parts of a litter box. While both models have carbon filters that need regular replacing, the Litter-Robot 4 is much more effective at trapping odors than the Litter-Robot 3 Connect, even with a full waste bag. Whisker says this is because the waste drawer is deeper and has a tighter seal.

I rarely smell any waste in the Litter-Robot 4—unless it’s fresh and still in the chamber before cycling. With the Litter-Robot 3 Connect, I can tell when it’s full just by the way it smells. It’s not as strong as an open litter box, to be sure, but things do get musky if you don’t keep up with cleaning. Whisker now sells OdorTrap packs that clip inside either drawer; they’re optional but noticeably help.

Sensors

The safety sensors also got an upgrade in the Litter-Robot 4. The Litter-Robot 3 Connect has weight sensors inside the globe that are triggered when your cat starts to enter or is inside the machine. These sensors stop or delay a cleaning cycle to keep your cat safe. While these have been reliable for me—the Litter-Robot 3 Connect has never, for example, cycled with my cat in the way—the sensors aren’t technically as effective as the ones in the Litter-Robot 4.

The newest version of the self-cleaning litter box has both laser and weight sensors so it can trigger the stop mechanism more readily, even if your cat is just peeking into the opening and hasn’t put their full weight into the globe. While this ensures a faster response time, it also means that cats who weigh just 3 pounds can safely use the Litter-Robot 4. For comparison, the minimum weight for the Litter-Robot 3 Connect is 5 pounds. The Litter-Robot 4’s SafeCat system pairs OmniSense lasers with weight plates, while SmartScale tech estimates which cat is inside based on weight data. Ongoing firmware updates have already dialed back oversensitivity, and each time the app prompts an update the unit gets a little smarter.

These sensors are also so advanced that they can tell you which cat in a multi-cat household is using the litter box. While the scale isn’t totally accurate—for example, it registers my 10-pound cat as weighing 7 pounds—it’s still a useful tool for tracking the bathroom habits of each of your pets. If one of your cats isn’t using the bathroom as often as they should (which can be a sign to call the vet), this feature can help alert you, says Jacob Zuppke, CEO and president of Whisker.

While the laser sensors make for a safer machine, they also make it more sensitive—I’ve had more accidental triggers with the Litter-Robot 4 than the Litter-Robot 3 Connect. Though those incidents can be annoying, Zuppke says the brand’s engineering team is always working behind the scenes to find the right level of sensitivity for these sensors. When I first got the Litter-Robot 4, the sensors were much touchier than they are now; thanks to firmware updates, they’re a bit less reactive. And the sensors aren’t the only part of the litter boxes the engineering team is constantly working on to improve. Any time you update one of the Wi-Fi–enabled models via the app, your litter box downloads any changes made. (It’s the same concept as iPhone updates.)

In addition to safety, the upgraded sensors have one other strength. When connected to the app, the Litter-Robot 3 Connect can only tell you if the waste drawer is full and needs to be emptied. Meanwhile, the sensors in the Litter-Robot 4 can monitor both waste and litter levels, so you can see exactly how full the waste drawer is and whether you need to add litter to the globe.

Noise

Noise, or lack thereof, is another major difference between these two models. The Litter-Robot 4 is significantly quieter than the 3 Connect—I can barely hear it when it’s running. The Litter-Robot 3 Connect isn’t obnoxiously loud, but I’d say it’s at least twice as loud as the Litter-Robot 4. (The sound level is about 50 decibels compared to roughly 25 decibels on the Litter-Robot 4’s QuietSift cycles; similar to an electric can opener or a bathroom fan.) For what it’s worth, the sound doesn’t bother my cats at all. If you have more skittish felines, though, you may want to upgrade to the Litter-Robot 4 just for this.

Deep Cleaning

Deep cleaning takes about the same amount of effort for each model, and Whisker recommends you do the chore at least every three months, depending on how many cats you have. To really get the litter box clean, you have to take everything apart, thoroughly wash it and then let all the parts dry completely before reassembling it. It also requires vacuuming where the waste drawer sits, and there are lots of nooks and crannies in each of the machines that make this a pain. It takes at least an hour to do every time, and neither machine has an edge here.

Price

Perhaps the most obvious difference between the Litter-Robot 3 Connect and the 4 is the price. The Litter‑Robot 3 Connect retails for $549, while the Litter‑Robot 4 is $699. Financing through Affirm brings the newest model to about $44 a month, and you can add an extended three‑year WhiskerCare plan for $100. In my opinion, the upgrades are worth the higher cost, especially when you consider how long these litter boxes are meant to last.

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Final Verdict

If it’s within your budget, I recommend purchasing the Litter-Robot 4. While I’m happy with the performance of both machines, the newer model’s design is such a massive upgrade. It’s considerably better with odor control, able to hold more waste and much quieter, which I believe are worth the extra cost.

Now, if you already own the Litter-Robot 3 Connect and it’s working well for you, I don’t think you need to toss it in favor of the Litter-Robot 4. If you want to add a second litter box, though, I’d go with the 4. And if you need more convincing, check out features director and cat mom Kim Peiffer’s full review of the Litter-Robot 4.

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Why Trust Forbes Vetted

I’m Lindsay Boyers, the executive strategy editor at Forbes Vetted and a self-proclaimed cat lady who has three Siberian cat mixes terrorizing (er, enriching) my home.

• I’ve owned the Litter-Robot 3 Connect for four years and the Litter-Robot 4 for a year and a half, and both are currently set up and used by my feline crew daily.
• In addition to relying on my personal experience with the Litter-Robots, I spoke with Jacob Zuppke, CEO of Whisker (the company that manufactures the Litter-Robot), to better understand how these models differ from each other and why the design changes were made.
• Beyond that, I’ve been testing pet products for more than five years. In addition to both Litter-Robot models, I’ve tested six other self-cleaning litter boxes.
• The Forbes Vetted home team has published numerous pet-related stories based on in-depth research and firsthand experience. Some of our top tested guides include the best cat litters, the best cat water fountains and the best cat trees.
• This story is regularly refreshed to ensure all information is accurate, both products are in stock and to add further testing insights. It was last updated in June 2025 by home and kitchen editor Kelly O’Sullivan.

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