Aqara Smart Lock U400: hands-free, Home Key and a real keyhole
The U400 is built around one trick: with a supported phone in your pocket, the door unlocks as you walk up. Around that trick sits a very complete lock, with every entry method a household might need.
By Quiet SwitchUpdated November 1, 2026No sponsored placementSpecs from maker documentation and the live listing
Buttons on this page are Amazon affiliate links: if you buy, Quiet Switch may earn a commission at no cost to you. Nobody pays for a position. How this works.
The Aqara Smart Lock U400 is worth buying for a household with mixed phones and a Thread border router near the door, because it offers hands-free UWB unlocking, Apple Home Key, fingerprint, keypad and a physical key, and works with Apple Home, Google Home and Alexa through Matter.
How this review was madeQuiet Switch does not own this device. This is a research review built from the maker's specifications and the product's Amazon listing, checked on October 29, 2026. Nothing here is written as though it had been tested in this house.
Best Smart Lock
Aqara Smart Lock U400
Thread
A main entrance in a household where not everyone carries the same brand of phone.
AlexaYes
GoogleYes
AppleYes
SmartThingsNo
Protocol
Matter over Thread
Entry
Fingerprint, keypad, Home Key
Keyhole
Physical key retained
UWB
Hands-free unlock on supported phones
Apple Home Key plus a fingerprint reader plus a keypad plus a physical key covers every member of a household including the one who refuses apps.
Matter over Thread means it answers to all three major platforms rather than one.
Ultra-wideband lets it unlock as a supported phone approaches, with no tap and no code, which is the feature that turns a smart lock from a gadget into a habit.
Skip this ifMost of the good features need a Thread border router in range of the door. Confirm coverage first.
A deadbolt replacement with Bluetooth 5.2, Thread with Matter 1.4, NFC and ultra-wideband radios, according to Aqara's FAQ on the Amazon listing. One long-form review by Derek Seaman describes it as the first smart lock with UWB support. Hands-free unlocking needs a phone with a UWB chip, which on the Apple side means recent iPhones.
Aqara sells a base model through retailers such as Amazon and a deluxe version through Apple, per the same review.
The three questions
Question
Answer
If the battery dies
A mechanical key cylinder is retained
Where the log lives
In the Aqara Home app, and in whichever Matter platform you share it to
Remote access
Over Thread, which needs a Thread border router within range of the door
Fit and installation notes
Aqara's FAQ says the lock supports all door-opening directions, uses a 60 or 70 mm deadbolt, and has an IP65-rated front panel. Check your door's thickness and backset against Aqara's guide before ordering.
Skip it if there is no Thread border router near the front door and no plan to add one: most of the clever features depend on it. The Schlage Encode Plus with built-in Wi-Fi is the simpler alternative.
FAQ
Questions people ask
Does the Aqara U400 work with Google Home and Alexa?
Yes, through Matter over Thread. Retail listings also name Apple Home and SmartThings.
Does hands-free unlocking work with Android?
UWB unlocking depends on the phone's UWB support and the platform. Check Aqara's current list of supported phones.
Quiet SwitchOne person, no sponsors, no devices owned. Specs come from maker documentation and the live listing; nothing here is written as though it had been tested in this house. How this site works →
