The Aqara Smart Lock U400 Detects When You Get Home, and Unlocks Itself—Hands-Free
I’ve experienced the future of smart locks, and I never want to go back
For the past two weeks, I’ve been unlocking my front door without ever touching a keypad, fingerprint reader, smartphone, or physical key, thanks to a new smart lock. It’s the first lock I’ve evaluated that feels so smart, it’s almost magic.
This hands-free unlocking is made possible by a new technology in smart locks called ultra-wideband (UWB) that can precisely detect when you approach a door.
The technology is already used in Apple AirTags, and it has been promised by lock companies for over a year, but the Aqara Smart Lock U400 is the first product to come to market with it. I’ve been evaluating the U400 ahead of its unveiling today at CES 2026 in Las Vegas. (The lock, $269.99, is now available to buy from Aqara.)
How a UWB Smart Lock Works
Hands-free unlocking isn’t new. Geofencing, which utilizes your phone’s GPS data to unlock your door, has been around for over a decade. But geofencing often covers a wide swath of territory, unlocking your door when you’re within several hundred feet of your home. For many people, that can feel unsafe. UWB is precise down to mere inches.
As you walk up to your door, the UWB radio in the Aqara smart lock helps determine the precise location of your UWB-enabled smartphone or smartwatch, and its distance and direction in relation to the lock. The lock will check that your device is authorized to unlock the door and do so once you get within a few feet.
The technology’s precision also lets the lock determine whether you’re inside or outside your house so that it doesn’t open every time you walk through your front hallway.
You'll Need Matter and Thread Hardware
The only downside to this experience, if you’re not a smart home nerd like me, is that you’ll need a good bit of hardware to get up and running.
The Aqara Smart Lock U400 uses the Matter standard to connect to smart home systems like Apple Home and Google Home, and it uses a relatively new low-power wireless network called Thread, instead of WiFi, to connect to the internet. (See my guide to Matter.)
This means you will need a Matter-compatible smart home hub and a Thread Border Router. However, many Matter hubs also work as Thread Border Routers, and you might already own one and not know it.
Popular home devices that work as Matter hubs and Thread Border Routers include recent Amazon Echo and Echo Show devices, Apple HomePod mini and HomePod 2nd generation, Apple TV 4K streaming media devices (2nd gen and newer), Eero mesh WiFi routers (WiFi 6 and newer), Google Nest Hub smart displays, Samsung SmartThings smart home hubs, and recent Samsung smart TVs and Family Hub refrigerators.
For the hands-free unlocking experience, you will need to use an Apple Matter hub, at least until the Aliro standard arrives.
This extra hardware requirement may be off-putting, but there are many benefits to Matter and Thread. For one, Matter devices work locally on your home network and don’t require a connection to the manufacturer’s servers to function, meaning they will keep working in the event of an internet outage or even if the manufacturer goes out of business. Matter devices that use Thread also have much longer battery life and respond faster to commands than their WiFi counterparts.
Setup Was Easy—With One Glitch
As someone who’s covered the smart home for over a decade, I’ve installed many smart locks. The installation process for the Aqara Smart Lock U400 was typical of what you’ll find with any smart lock. The only minor problem I encountered was some extra slack in one of the wires connecting the exterior and interior sides of the lock, but I was able to carefully push the excess wire into the bore hole and firmly attach the interior side of the lock to the door.
Thanks to Matter, I was able to set up the Aqara Smart Lock U400 entirely in the Apple Home app and even update its firmware without ever opening the Aqara app. The Apple Home app walked me through the process of naming the lock and adding it to a room in my home. It also made it easy to enable Apple’s Express Mode, which allows your iPhone or Apple Watch to unlock the door without additional authentication, such as scanning your face.
Source: Apple Source: Apple
However, I ran into an issue when trying to create access codes for the lock’s keypad in Apple Home.
Somehow, I already had an access code assigned to my account, which I can use to manually open the door. I can share that code with my wife, of course, but I haven’t been able to create separate access codes for other people. To see whether this was an issue with the lock or Apple Home, I also connected it to Google Home, Samsung SmartThings, and the Aqara app. I was able to create a code for myself in Google Home, but I couldn’t create additional codes. And I wasn’t even able to open the access code section of the SmartThings app—for any smart lock, not just this Aqara. I was able to create multiple codes in the Aqara app, but one of the goals of Matter is to save people from needing to use multiple apps.
I’d like to tell you this kind of glitch is unusual, but it’s not. Welcome to the smart home, where things are supposed to “just work” and often never do. I contacted Aqara about the access code issue, and a company representative said to try deleting my old lock from Apple Home. Sure enough, that fixed the problem, and I was able to create multiple access codes in Apple Home. But the issue persisted with Google Home and SmartThings, even after deleting my old lock from those systems.
Once setup was complete, I started using the lock, including the UWB hands-free unlocking. I was pleasantly surprised to learn that this feature was automatically enabled on my wife’s phone, who already had access to our shared Apple Home setup. She loves the new feature—and it’s rare that she finds any of our smart home gear impressive.
Bottom Line: This UWB Smart Lock Really Is Smart
The access codes aside, this is the best experience I’ve ever had with a smart lock, and I’m not pleased to go back to my old one. There’s no need to think about unlocking my front door; it just happens on its own.
We’ll probably see a few more UWB-enabled smart locks arrive this year. You can expect variations on the theme, as well. For example, a new company called Doma, founded by the creators of the popular August Smart Lock, is working on smart motorized doors. Imagine walking up to your front door and having it not only unlock on its own, but open for you too. Now that would be smart.
Then there’s Durin, another new company working on a device that would bring hands-free unlocking to existing smart locks that lack the UWB hardware.
With the Aliro standard arriving soon, this tech can all move beyond Apple’s walled garden, coming to more smartphones, smartwatches, and smart locks.
