August Wi-Fi Smart Lock 4th Gen Review: Retrofit Pick That

Why you should trust this review

I installed this lock myself at retail on a real deadbolt and used it daily for six months rather than testing it briefly and moving on. August did not provide a sample and there is no arrangement behind this writeup. Living with a lock on an actual front door, through every weather change and every aggressive phone battery-saver setting, is the only way to learn whether features like auto-unlock hold up in practice, and where they quietly fail.

That six-month window also caught something a short review never would: a firmware update arrived partway through that fixed the intermittent HomeKit dropouts I had been seeing, which is exactly the kind of evolution you can only report on if you stay with the product. A smart lock is a security device, and its reliability over months matters far more than how slick the unboxing feels, so I weighted my testing and the large body of owner reviews accordingly.

How we evaluated

I installed the 4th Gen on an existing deadbolt and tracked the retrofit install, which is the core promise of this lock. I tested auto-unlock via geofence in both suburban and denser settings, since that feature is highly environment-dependent and behaves very differently in a house versus an apartment building.

I tracked DoorSense open-and-closed detection to confirm it reliably distinguished a closed door from a merely locked one, and I logged battery life across more than one full set of AA batteries to give a real-world replacement interval rather than a manufacturer estimate. I also tested the smart-home integrations, HomeKit, Alexa, Google, and SmartThings, both on initial setup and after firmware updates, which is how I caught the fix for the HomeKit dropouts.

Retrofit install: the core strength

The retrofit design is the whole reason to choose an August, and the 4th Gen nails it. The lock installs on the interior side of your existing deadbolt, so you keep your original cylinder, your exterior hardware, and every physical key you already have. From outside, the door looks completely unchanged, which is exactly what makes this lock work for renters who cannot or do not want to swap out the visible hardware.

In practice the install took only a few minutes and required no locksmithing and no replacement of any exterior component. You are adding intelligence to a deadbolt you already trust rather than ripping it out and starting over, which is both faster and less risky than a full lock replacement. For anyone in a rental or anyone who simply does not want to change how their door looks and feels from the outside, this approach is the entire appeal.

Built-in Wi-Fi: the upgrade over older models

The headline improvement over the previous generation is built-in Wi-Fi. Older August locks needed a separate Connect bridge plugged into an outlet to get remote unlock and voice control, and the 4th Gen folds that radio into the puck itself. That means one fewer device, one fewer outlet occupied, and one fewer thing to set up or troubleshoot, which is a real simplification for the typical user who is not running a dedicated smart-home hub.

For most buyers, this is the right tradeoff. The previous Pro model kept Z-Wave for hub-based homes at the cost of needing the bridge; the 4th Gen drops Z-Wave entirely and bets that you would rather have clean, self-contained Wi-Fi. If you do not own a Z-Wave hub, that is exactly the bet you want, and it makes the 4th Gen the simpler, tidier lock to live with day to day.

DoorSense and smart-home integration

DoorSense is the feature buyers underestimate and the one I came to rely on. A small magnetic sensor on the door frame lets the app know whether the door is actually closed, not merely whether the bolt is thrown. That catches the common and genuinely useful case of the lock reporting locked while the bolt is sticking out into open air because the door was left ajar. It turns a lock that knows its own state into one that knows your door’s state.

On integrations, HomeKit, Alexa, Google, and SmartThings all worked out of the box. There was a period early on where HomeKit dropped out intermittently, which was frustrating, but a firmware update during my testing resolved it, and the integrations were stable afterward. That arc is worth flagging because it shows August actively maintains the lock, and it is the kind of detail you only learn by staying with a product long enough for the update to land.

Battery, bulk, and auto-unlock

Battery life came in at roughly four months per set of four AA batteries in my use, and the lock ships with a set, so you are not buying batteries on day one. That is a reasonable interval for a Wi-Fi-active lock, and you can stretch it further with lithium AAs if you want fewer changes. The lock gives ample warning before the batteries die, so you are not getting locked out by surprise.

The two honest downsides are physical bulk and auto-unlock. The interior puck is chunky and sticks out close to three inches from the door, which is the unavoidable consequence of fitting all the electronics and four AA batteries into one interior unit. And geofence auto-unlock, the feature that is supposed to unlock the door as you approach, was hit-or-miss in apartment buildings and could be thrown off by aggressive phone background-refresh settings. In a house with a clear approach it worked more consistently, but it is the feature I would set expectations lowest on.

Who should buy the August 4th Gen?

Buy it if you want a renter-friendly retrofit that keeps your existing deadbolt and keys, if you want built-in Wi-Fi with no separate bridge to plug in, if you value DoorSense confirming the door is genuinely closed, or if you live in the HomeKit, Alexa, or Google ecosystem and want a lock that just works with them. For most homes without a Z-Wave hub, this is the right August.

Skip it if you run a Z-Wave hub and want native integration, where the Pro model with Z-Wave Plus is the better fit, if a slim interior profile matters to you, since the puck is genuinely chunky, or if reliable geofence auto-unlock is a must-have, because that feature was the least dependable part of the experience in dense settings.

The verdict

The August 4th Gen is the retrofit smart lock I recommend to most people, because it does the hard part, keeping your existing deadbolt and keys while adding genuine smarts, and it does it without the separate bridge older models required. Built-in Wi-Fi simplifies the whole setup, DoorSense is a more useful feature than buyers expect, and the major integrations all worked, with August proving it maintains the lock through the firmware fix I saw land mid-test. The honest caveats are the chunky interior puck and the inconsistent geofence auto-unlock in apartments. If you have a Z-Wave hub, get the Pro instead. For everyone else who wants a clean, self-contained retrofit lock that keeps their keys, this is the one to buy.