Aqara Smart Lock U400

The premium buys fewer things to do at the door

U400's distinctive feature is unlocking as you approach with a supported iPhone or Apple Watch. Carrying groceries is a better reason to want that than collecting another smart-home logo. When it works for your device and doorway, there is no keypad to press and no phone to take out.

The lock also has a fingerprint reader, PIN keypad, NFC access and two physical keys. Those are important everyday alternatives because a household may mix phones, forget a device or prefer a deliberate tap.

We have not tested UWB accuracy or unwanted-unlock behavior. Aqara says the system uses distance and direction to distinguish an approach from passing nearby; that is its design claim, not a guarantee from us about your entrance.

An iPhone name alone does not establish support

Hands-free entry needs Ultra Wideband hardware and the supported Apple home setup. Aqara lists UWB-equipped iPhone 11 and later with iOS 18.5+, or Apple Watch Series 6 and later excluding SE with watchOS 11.5+, plus a Thread-enabled Apple home hub.

The exclusions matter. iPhone SE, iPhone 16e and iPhone 17e lack the required UWB hardware; Apple confirms the 17e exclusion even though Aqara's older list stops at 16e. A phone can support NFC home key taps without supporting approach unlocking. Do not budget for U400's main attraction until the specific phone or Watch qualifies.

Samsung owners get a different result. Aqara released Samsung Wallet NFC home keys with U400 firmware v3104 in March 2026, using supported Galaxy phones and SmartThings. But on August 28, Aqara said Samsung UWB unlocking remained in development with no revised date. A Samsung phone's UWB chip or the lock's Aliro certification does not make that delayed feature available.

Charging is flexible, but low battery changes the experience

The removable lithium battery can charge inside the lock through its interior USB-C port, or separately after removal. Charging in place avoids taking the electronics offline; removing the only battery leaves the mechanical key as the fallback.

The exterior USB-C port supplies emergency power rather than recharging the battery. Aqara also advises against leaving the interior charging port powered continuously during normal use. This remains a battery-maintained lock, not a permanently wired one.

The current manual says UWB automatically switches off below 8% battery. That means the headline convenience disappears before the battery is completely exhausted. Aqara's up-to-six-month battery estimate is not a result we have measured.

Compare packages carefully. Aqara lists standard one-battery models, models bundled with M100, and separate two-battery versions. The $269.99 US standard listing should not be assumed to include either extra. An M100 bundle also does not replace the Apple home hub needed for Apple's hands-free path.

A full replacement needs to suit the door

U400 replaces a compatible single-cylinder deadbolt. The manual covers 60 or 70 mm backsets and 35–55 mm door thickness. It shows 38 or 54 mm bores, but says a solid door with the smaller opening needs enlargement; the small-bore option is not universally interchangeable.

The lock cylinder is rekeyable, which can be useful when matching physical access matters. Whether it can share a particular existing key still depends on the cylinder and key system. Installation or locksmith work can raise the cost beyond the lock.

Its IP65 rating applies to the exterior panel. The interior thumb turn provides a physical way to operate the deadbolt, while Aqara Home adds auto-lock timing and other detailed settings. Matter shares lock control with supported ecosystems; it does not make every Wallet feature or access-management setting identical.

Worth $100 more than a retrofit only if you use it

On September 10, 2026, black and silver U400 standard locks were $269.99 at Aqara's US store, qualifying for free standard contiguous-US/DC delivery before tax. Installation and any missing home hub remain additional costs.

For a compatible US deadbolt worth retaining, U200 was $169.99 with a separate fingerprint keypad and Apple home key taps. It saves $100 in hardware and keeps the existing cylinder, but does not provide U400's UWB experience.

Choose U400 for supported hands-free entry and a door ready for a full replacement. Keep an existing lock if a fingerprint, PIN or tap already feels easy. Buying now for a delayed Samsung feature is a weaker case than buying for a benefit the household can use today.