Buying
Retrofit smart locks turn the thumbturn you already have. Nothing is drilled, the cylinder stays, the key still works, and the door goes back as it was. What they change is who can open it and when — and not, in any respect, how hard it is to force.
There are two products called a smart lock and only one of them suits a tenant.
A retrofit mounts on the inside and turns your existing thumbturn, or the key left in the cylinder. A replacement takes over the cylinder itself, which a lease rarely permits and which changes the key everybody holds.
Depending on the lock, a thumbturn on the inside with clearance around it (Aqara U200, SwitchBot Lock Ultra), or a cylinder with an emergency function, which opens from outside even with a key left in on the inside (the locks that turn that key, such as the Nuki). Check the lock’s compatibility list: a new cylinder costs a fraction of the lock, but it is itself a change to ask about.
An open protocol. A lock speaking Matter joins Apple Home, Google Home or Alexa directly and does not depend on one company continuing to run a service. On a device you keep for years, that matters more than the number of unlocking methods.
It is convenience and control. Not resistance.
The main appeal, and the thing people actually notice day to day.
Where granting and revoking access without cutting keys is genuinely useful.
Where an access log answers questions a physical key never could.
Where reversibility and the landlord's continued access decide what is possible.
| Your need | The type | The check |
|---|---|---|
| Landlord keeps a key | Retrofit thumbturn lock | Existing cylinder untouched |
| Temporary access | App-based sharing | Revoking must be easy |
| Battery worry | Key still works | Ask before buying |
| Moving out | Fully reversible | No trace left |
Smart locks add a second failure mode to a door: the mechanism and the electronics. Batteries in a cold hallway last less than expected, and a lock that has been warning for weeks eventually stops turning at the least convenient moment.
A smart lock is a lock and an account.
Retrofit · built-in Wi-Fi, no bridge · Matter over Thread · charged at the door · months per charge
Nuki's fifth-generation lock puts Wi-Fi inside the unit, so remote access needs no bridge or hub, and adds Matter alongside Bluetooth. The battery charges at the door with the supplied cable rather than coming off it.
Best for: A household that wants remote access without adding another box to the hallway.
Matter over Thread · Apple Home Key · rechargeable Li-ion, 6 months stated · no drilling
A retrofit lock with native Matter over Thread, so it joins Apple Home, Google Home and Alexa without a vendor bridge. Aqara states Apple Home Key support, a rechargeable battery quoted at up to six months, and a quiet unlocking mode.
Best for: A household already running Matter or Apple Home, that wants the lock to be part of it rather than another app.
Retrofit · fingerprint, app and Bluetooth · magnetic auto-lock · 6 cells · no drilling
A retrofit lock that mounts over an existing cylinder with no drilling and no cylinder change. Signstek states fingerprint, app and Bluetooth access, magnetic auto-locking, and six batteries; the existing key still works from outside.
Best for: A first smart lock, and particularly a rented apartment where nothing may be altered.
No. It turns the thumbturn. The cylinder, the strike plate and the frame are exactly as they were, and those are what resist force. If the door is the weak point, the money belongs in a cylinder and long screws rather than here.
Your key still opens the door, because the cylinder was never touched. That is the structural advantage of retrofit locks over replacement ones — and it only helps if the key is somewhere other than inside the locked flat.
Often yes, with a retrofit type that fits over the interior thumbturn and leaves the exterior cylinder and the landlord's key untouched.
Check the lease. A retrofit lock that changes nothing externally is usually far easier to get agreed than a cylinder change.
Through the app, which is the genuine advantage over keys. Make sure revoking is as easy as granting before you rely on it.
It now opens your front door. Treat it accordingly: a strong unique password and a second factor wherever it is offered.
Designed for: A household that wants remote access without adding another box to the hallway.
Its main asset: Wi-Fi built in — no bridge, no hub, no extra socket
Its main gap: Nothing listed on amazon.com, so this lock cannot be priced against the shelf
Designed for: A household already running Matter or Apple Home, that wants the lock to be part of it rather than another app.
Its main asset: Native Matter over Thread — no proprietary bridge, and it works across ecosystems
Its main gap: Thread needs a border router in the house — an Apple TV, HomePod or equivalent
Designed for: A first smart lock, and particularly a rented apartment where nothing may be altered.
Its main asset: Retrofit: no drilling, no cylinder change, and the door goes back as it was
Its main gap: Six cells to keep track of, and no published runtime assumption
$60 – $80
3 models
$80 – $170
5 models
Device against device, already covered, inside this guide or this aisle.
The devices listed are drawn from the catalog of this site. Specifications are those the maker and the Amazon listing publish; prices are what Keepa recorded on the date shown, and both move. The order follows declared specifications, the balance between stated strengths and stated limits, and price. No device here has been installed or tested by us, and no page claims it was.
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Prices quoted in these summaries are dated readings. The live price is shown next to each product.
Cameras, alarm kits and safes swing by thirty dollars or more across the year, and the biggest "discounts" often land at prices the same model sold for six weeks earlier. UniverTrack tracks the real price history across retailers, spots fake reductions, and alerts you when it is genuinely the moment to buy.
