The U400 launch has been met with a lot of excitement - and also a lot of questions as I’ve seen users all over the internet raising different concerns. Kudos the Aqara team for listening to their customers so well and responding to these directly, and providing updates/fixes. No doubt a lot of work went into developing the U400 and now fine tuning comes with more real-world usage.
That said, I’ve had a great experience in my use of the U400. It’s such a fun lock and is working really well for my family.
I’ve been testing the Aqara U400 for a while now and wanted to share some real-world observations that might help others who are either considering it or already installing one.
Ultra Wideband Unlock: What’s Actually New Here
The headline feature with the U400 is Ultra Wideband (UWB), specifically when used with Apple Home Key. Unlike NFC tap-to-unlock, UWB enables unlock on approach, meaning the door can unlock automatically as you walk up — no fiddling with keys, phones, or fingerprint readers.
In daily use, this has been surprisingly reliable. The key detail is configuring approach direction correctly. If your door is near an interior wall or hallway, choosing the wrong direction can cause unlocks when walking inside the house. Once dialed in, though, it’s been seamless.
Hardware & Build Quality
The lock itself feels solid and premium. It is larger than some previous Aqara models, but that’s largely due to the rechargeable battery cartridge and added radios. The keypad has a matte finish that resists fingerprints well, and the lock installs like a standard deadbolt.
Fingerprint unlock works well, though I still find lever-style readers (like on the U300) more natural ergonomically.
Important Setup Tip: Strike Plate Alignment
One issue I’m seeing come up online — and that I can reproduce — is the lock feeling “tight” or like the motor is straining.
In most cases, this comes down to strike plate alignment.
Aqara includes a strike plate in the box, but many people reuse their existing one to avoid chiseling. If the bolt doesn’t have enough clearance to fully extend and retract without resistance, the motor ends up working harder than it should. You can actually feel and hear the difference when the bolt is slightly jammed.
The fix is simple:
- Make sure the bolt moves freely with the door closed
- Ensure full extension without friction
Aqara has also released a firmware update that increases motor torque to help overcome minor resistance, but proper alignment is still critical for long-term reliability.
Battery Life So Far
Battery life has been excellent in my testing. Aqara rates it at around six months with regular use, and the battery is USB-C rechargeable. I’ve seen comments on other threads that Aqara is planning on how to sell extra batteries, making them hot-swappable.
Ecosystem Support & Matter
The U400 supports Matter over Thread and Bluetooth. You don’t need an Aqara hub if you already have a Thread border router (Apple TV, HomePod, etc.), though the Aqara app does unlock some additional ecosystem features.
Apple Home currently gets the most out of this lock, especially with UWB. Other platforms (Home Assistant, Alexa, Homey) support core lock/unlock functionality, but don’t have access to UWB-specific features since those are OS-level integrations.
The lock is also Aliro-ready, but personally I wouldn’t buy it today solely on that promise until the standard rolls out more broadly.
Who I Think This Lock Is For
Right now, the U400 makes the most sense for:
- Apple Home users
- Aqara ecosystem users
- Anyone excited about hands-free access and future-facing standards
- Eventually the rest of the smart home community as Aliro rolls out and more phones support UWB.
I put together a full video walkthrough covering unlock-on-approach behavior, setup tips, automations, and comparisons if anyone wants a deeper look: https://youtu.be/Fn3RGM09vwI
Happy to answer questions here as well — especially around setup or Apple Home behavior.
And if you have a U400 success story, feel free to share that too!
We are glad that U400 brings you good experience.