Hands-on with Aqara’s U400 – the first smart lock with Apple’s UWB Home Key

Aqara has announced a new smart deadbolt lock at CES this week. The U400 ($269.99) is the first to support Apple’s Home Key’s hands-free unlocking. This uses the U1 ultra-wideband (UWB) chip in many iPhones and Apple Watches to automatically unlock your door as you approach — no physical interaction required. I tested the U400 at my home earlier this month, and it’s been a significant upgrade for my front door.

I still have to physically open the door, but there’s no need to punch in a code, use a fingerprint, pull out my phone, or bring my watch up to the lock; the door is unlocked by the time I get there. This makes it faster and easier to get into my house when my hands are full, if I’m wearing gloves, or if I’m just in a hurry.

Hands-free unlocking isn’t new; I’ve tested several proprietary systems on locks from Yale, August, Level, and others. What’s different is the tech. Most existing systems use a mix of Bluetooth, Wi-Fi, and geofencing and rely on you having an app running on your phone. I’ve also found them to be unreliable, often leaving me standing in front of a locked door waiting for it to open.

Apple’s implementation uses Bluetooth and UWB to establish a direct connection between the lock and the phone — no app required. In my week of testing, it has worked every time without any waiting. Well, other than one incident when I had my phone under a pizza box. It still unlocked, but a beat after I arrived at the door.

UWB is a short-range, low-power technology that uses short pulses across a wide frequency band and is designed for secure, real-time location, distance, and direction measurements. It’s already widely used to unlock cars. The technology is precise enough to understand which angle you are approaching from, so it won’t unlock if you’re inside the house or just walking past the front door.

UWB unlocking is part of Apple Home Key, a feature of Apple’s Home app that lets you use your iPhone or Apple Watch as a key for your door when used with a compatible smart lock. Home Key locks that use NFC tap-to-unlock have been available since 2022, and we’ve tested several. Apple introduced UWB unlocking capability when iOS 18 launched in 2024, but there have been no compatible locks until now.

I expect we’ll soon start to see more locks supporting it. UWB is part of a new universal smart lock standard called Aliro, being developed by Apple, Samsung, Google, and major lock manufacturers. Aliro is designed to bring both UWB and NFC unlocking to other smart home platforms and devices beyond Apple. This includes Samsung Galaxy and Google Pixel phones and watches. The U400 is Aliro-ready, and the standard — announced in 2023 — is launching this year.

At CES last year, a couple of UWB locks were announced, including ones from Schlage and U-tec. However, Aqara’s U400 is the first to confirm support for Apple’s Home Key implementation.

The U400 is a full-replacement deadbolt smart lock that, along with Home Key (NFC or UWB), can be unlocked using a code on its touchscreen keypad, a fingerprint reader, or a traditional key. It’s a Matter-over-Thread lock, so you can control it with any Matter-compatible smart home app to add it to scenes and control it with a voice assistant. It also works with Aqara’s app via Bluetooth.

The U400 has a built-in gyroscope that tells it whether the door is open or closed, and it can be set to automatically lock when closed. It’s IP65-rated and comes with a single 4,880mAh rechargeable battery, which Aqara says will last six months on a single charge. That’s on the low side for a Thread-powered lock, but UWB is a fairly power-hungry radio for a battery-powered device.

Installing and setting up the U400 was straightforward and similar to most smart locks, other than the addition of a second data cable, which appears to power the UWB radio and antenna. The lock is larger and taller than Aqara’s other models, probably to accommodate the extra tech.

I tested the silver model, and like most of Aqara’s devices, it’s more functional than design-forward. I’m not a fan of the Aqara logo at the bottom, and the large black touchscreen showed fingerprints right away. The exterior is aluminium and has a solid feel, but the large rear housing is all plastic.

I connected the lock to the Apple Home app by scanning the Matter code, and it onboarded smoothly. (It’s a Thread lock, so you need a Thread border router.) I already have Home Key set up, and Apple Home prompted me to use it with the U400 and to turn on Express Mode.

This bypasses having to use Face or Touch ID to unlock a door, and it’s required for hands-free unlocking. While it unlocks using UWB, the U400 connects to your phone first via Bluetooth. Interestingly, the lock stayed connected to my Bluetooth whenever I was in the house.

Because Home Key works with every member of my Apple Home household, my family’s iPhones all got updated to work with the U400 automatically. However, I had to activate Express Mode on each phone individually in the Home app and turn on Unlock on Approach on the Home Key in their Apple Wallet to get hands-free unlocking to work.

You can add access codes to the lock via Apple Home, and the touchscreen keypad was responsive and easy to use. It’s very large, which means the numbers are well spaced, so it’s easy to hit the right buttons.

If you connect the lock to the Aqara app, you can add codes and fingerprints. The fingerprint reader was fast and responsive, and it’s a good backup for when you don’t have your phone on you.

I’ve been looking forward to UWB hands-free unlocking and its promise of a seamless, secure, and speedy way to unlock your door. Based on my experience so far, Aqara’s U400 delivers on that promise. While the lock is larger and less refined than some existing smart locks, Home Key UWB’s reliability and speed offer an exciting glimpse of where smart locks are headed.

Photos and video by Jennifer Pattison Tuohy / The Verge