Aqara U400 review: Made for Apple Home

Smart locks have gotten progressively more convenient, adding features like fingerprint sensors, palm vein readers, and more app-based controls. These are all well and good, but there's one problem with them -- they all still require you to actively do something. The Aqara Smart Lock U400 changes that equation with ultra-wideband (UWB) support for Apple Home Key, allowing the lock to detect your approach and unlock automatically just by knowing it's you.

Aqara has carved out a solid reputation among smart home enthusiasts, especially those deep in the Apple ecosystem. The company has been steadily broadening its device compatibility through Matter support, which means its products now play nicely with Google Home, Amazon Alexa, Samsung SmartThings, and Home Assistant. The U400 is Aqara's most feature-packed lock to date. But does UWB live up to its promises as one of the best smart locks?

Aqara U400 review: Price and availability

The Aqara U400 is now available from the Aqara website, as well as other participating retailers, like Amazon. It comes at $269.99, and is only available in Black.

Aqara U400 review: Design and setup

The U400 is relatively sleek and stylish from an aesthetic standpoint, though there's no mistaking it for a traditional deadbolt -- it clearly looks like a smart gadget. That's not necessarily a bad thing, of course. The footprint is larger than a conventional lock, but it should fit in reasonably well with most door designs. The exterior panel keeps the keypad hidden when you're not using it, which helps maintain a cleaner look. A fingerprint sensor sits below the keypad, and a small UWB indicator in the bottom left corner lights up when the lock senses you approaching.

Unlike smart locks that retrofit onto your existing deadbolt, the U400 replaces the entire assembly, which means installation takes a bit more effort. The lock works with standard doors, and the exterior keypad has an IP65 water-resistance rating, so it can handle being on a door that faces the elements.

On the inside, you'll find a removable rechargeable battery, a thumb latch for manual control, and buttons for initial setup, hidden under a cover. Aqara says the battery should last around six months, which isn't terrible, but nothing to write home about either. When the battery eventually dies, you can remove it and charge it via a built-in USB-C port, and if you're gone when it loses power, you can use the USB-C port connected to an external power bank or even your phone to get inside.

Setting up the U400 is straightforward. The Aqara app guides you through the process step by step, and printed instructions come in the box. After you've got the physical hardware installed, you'll need to configure it on your phone. Since the U400 is a Matter device, you're free to set it up in whatever smart home platform you prefer rather than being stuck with Aqara's software -- though you will need a Thread border router for most features. The lock technically functions over Bluetooth alone, but buying this particular lock for Bluetooth-only use kind of defeats the purpose.

The lock offers a range of locking and unlocking features, which is nice. It can store up to 50 fingerprints and 75 PIN codes ranging from 6 to 10 digits. It also supports NFC cards if you want to use them -- though you'll need to buy those separately since none come in the box. And, it works with a good ol' fashioned key.

Unlike other smart locks, which might have a PIN pad as a backup to a fingerprint sensor, it's the fingerprint sensor that's the backup -- and the PIN pad is the backup to the backup. Of course, the PIN pad also comes in handy for things like guest codes, however you can also share Home Key access in Apple Home.

Aqara U400 review: App

While you don't have to use the lock with Aqara's app, you'll probably want to download the app to set up things like fingerprints. You can set up codes and guest codes in other smart home apps, but the fingerprint sensor will need to be set up through Aqara.

For the most part, the app has a clean, easy-to-navigate interface. Managing the lock through the app is simple enough, though if you're already set up in another ecosystem like Apple Home, you'll probably do most of your day-to-day interaction there instead, especially since it also supports features like auto-locking. There is an auto-lock feature in the Aqara app that's supposed to be able to detect when you close your door and lock immediately, which worked most of the time, but sometimes took more than a few seconds when I tested it.

It's a neat idea, but it's worth having the time-based auto-lock feature enabled too, as a backup, even if it means you might occasionally find the door locks on its own when you haven't closed the door yet.

User management works differently depending on whether you're using Aqara's system or Matter. Through Aqara, you can set up to 100 users with detailed control over admin, standard, and temporary roles. Matter caps you at 20 users with up to 35 passwords of 4 to 8 digits, 35 NFC devices, and 20 UWB devices. For most households, either limit should be plenty.

Aqara U400 review: Connectivity and performance

The U400 supports Thread with Matter 1.4, Bluetooth 5.2, NFC, and ultra-wideband. That means that it'll work with all major smart home platforms -- however you will need a Thread border router to be able to control most functions of the lock.

Connectivity held up well in my testing. I installed the lock on my garden shed at the back of my backyard -- an area that usually has pretty weak wireless coverage. Despite the challenging location, the lock performed solidly. It's also worth pointing out that fingerprint and UWB unlocking don't need network connectivity to work. They operate locally regardless of what's happening with your home network.

The UWB hands-free unlocking worked quite well — honestly better than I expected. The lock detected my approach and unlocked consistently almost every time. There were occasional moments where it took an extra second to register when I only had my Apple Watch and not my phone, but this rarely became an actual problem. Even when that happened, the delay was about the same as the time it would take to use the fingerprint sensor anyway.

That reliability is kind of a big deal. Up until now, smart locks have given you more ways to unlock your door without a physical key, but they've still needed you to do something, or provided clunky workarounds, like geo-fencing that often unlocks the door when you're within a relatively large area. With UWB support, as long as you've got a compatible phone or smartwatch on you, the U400 unlocks without any action on your part whatsoever.

The other unlock methods worked well too. The fingerprint sensor was quick and accurate. The PIN pad, by comparison, sometimes took a few taps to turn on, but then worked fine. To be fair, I only really used it during initial testing and setup. In actual daily use, I never touched it. Even if UWB completely failed for some reason, the fingerprint sensor would have been my go-to backup, not the keypad.

Last but not least, there’s NFC. While you won’t get NFC cards in the box, you can still use your phone or watch with Apple Home Key through NFC, which worked well.

Aqara U400 review: Verdict

The whole promise of smart home technology has always been that your home can work without requiring your active involvement. UWB makes that promise real for smart locks in a way that fingerprint sensors and PIN codes never could, and in a way that's yet to come to other kinds of smart devices in any real way.

For the time being, while the Aqara U400 works well with any major smart home ecosystem thanks to Matter support, it's best suited for Apple users who can fully leverage the UWB Home Key functionality. If you're not in the Apple ecosystem or don't have a compatible device for hands-free unlocking, there are plenty of fingerprint-enabled smart locks that will serve you nearly as well. But for those who can use it the way it's meant to be used, the U400 makes a serious case for itself as the smart lock to beat for those who don't want to have to manually lock and unlock their door. Sure, it’s a little pricey – but for now, it’s the price you’ll have to pay if you want a lock that supports UWB.