August Lock Pro 4th Gen: Built-In Wi-Fi, DoorSense, Z-Wave Plus

The August Lock Pro 4th Gen is a retrofit smart deadbolt that sits entirely on the inside of your door. You keep your existing deadbolt cylinder, your exterior hardware, and your physical keys. August clips over the interior thumb-turn using one of the included adapters, so installation takes about 10 to 15 minutes and a screwdriver. Nothing visible changes on the exterior of your door. This review covers the install, daily use, and where the retrofit approach falls short.

This is the fourth-generation model (AUG-SL04-M02-G0X). It builds on the Wi-Fi Pro with a cleaner housing design, improved Z-Wave Plus radio, and refined DoorSense detection. At $229, it's August's flagship retrofit lock for households that want full smart home integration without replacing the entire deadbolt.

What's Different About the 4th Gen

The headline change from earlier August Wi-Fi models is Z-Wave Plus alongside built-in Wi-Fi. Previous Pro versions had one or the other. The 4th Gen ships with both radios active, which means you can connect it directly to SmartThings, Wink, or Ring Alarm through Z-Wave without a separate hub, and still get remote access through Wi-Fi and the August app.

DoorSense is included in the box. The magnetic sensor mounts on the door frame with double-sided tape and detects physical door position independently from the deadbolt. It's a small but practical feature: a door that swings ajar in a breeze won't trigger auto-lock and throw the bolt into an open frame.

Key Specs at a Glance

• Retrofit design: fits over existing interior thumb-turn, no drilling required
• Connectivity: 2.4 GHz Wi-Fi + Bluetooth + Z-Wave Plus
• Voice assistants: Alexa, Google Assistant, Siri via HomeKit
• Smart home platforms: Apple HomeKit, SmartThings, Ring Alarm, Wink, Google Home
• DoorSense: door open/closed detection included, sensor in box
• Battery: 4x AA (approximately 6 months typical use)
• Guest access: time-limited virtual keys via the August app
• Price: $229

Installation and Setup

Installation starts with removing the existing interior thumb-turn assembly and choosing the correct August adapter for your deadbolt. August ships adapters for the most common American deadbolt configurations, and the app walks through each step with illustrated instructions.

Wi-Fi pairing runs through Bluetooth first. The lock pairs to your phone via Bluetooth, then you select your 2.4 GHz network and enter the password in the August app. 5 GHz is not supported, which is standard for battery-powered smart home hardware. The full process from unboxing to remote access typically takes under 20 minutes.

Z-Wave Plus pairing is separate and optional. If you use SmartThings or Ring Alarm, you put your hub in inclusion mode and hold the August button as directed. August's official setup guide walks through both pairing methods in detail.

App Experience and Guest Access

The August app covers everything: lock, unlock, view the activity log, manage guest keys, and configure auto-lock timing. Guest access is one of the strongest parts of the experience. You send a virtual key from the app, set the date range and time window (a specific weekend, every Monday 9-11 AM, or permanent access), and the guest receives a notification to download August and accept the key. You revoke access instantly without touching the lock.

The activity log shows every lock and unlock event with timestamp and who triggered it, whether that's a family member's app, a guest key, auto-lock, or a voice assistant command. This audit trail is genuinely useful for households with multiple people coming and going.

Auto-Lock and Auto-Unlock

Auto-lock engages the deadbolt after a delay you set in the app, from 30 seconds to 30 minutes. DoorSense integration means auto-lock only fires when the door is fully closed. That combination prevents the deadbolt from engaging while the door is partially open, which would damage the strike plate.

Auto-unlock uses phone geofencing combined with Bluetooth proximity detection. The app triggers when your location crosses a boundary around your home, then waits for Bluetooth confirmation at close range before unlocking. The two-step approach reduces false unlocks from driving or walking past the house.

Smart Home Integrations

Z-Wave Plus and SmartThings

Z-Wave Plus is the standout addition on the 4th Gen. SmartThings users can pair the August lock directly and include it in SmartThings automations, routines, and scenes alongside other Z-Wave or Zigbee devices. Ring Alarm works the same way through its Z-Wave hub. Lock and unlock events feed into Ring's dashboard and can trigger Ring camera recording or alarm responses.

Apple HomeKit

HomeKit integration is native. Add the lock to the Home app by scanning the HomeKit code on the packaging, then control it with Siri, include it in HomeKit automations, and check status in Control Center. Households with multiple iOS devices get the most out of this: the lock appears in everyone's Home app once added to the home.

Home Assistant

Two integration paths exist. The cloud-based August integration connects through your August account and surfaces lock state and activity in Home Assistant. For local control, pair the lock to a Z-Wave JS USB stick and use the Z-Wave JS integration. Local Z-Wave gives faster response, no cloud dependency, and keeps all lock activity on your local network.

Pros and Cons

What works well:

• Retrofit design leaves exterior hardware completely unchanged
• Z-Wave Plus covers SmartThings and Ring Alarm without an extra hub
• DoorSense prevents auto-lock mishaps with an open door
• Guest access management is clean and practical
• Works with HomeKit, Alexa, Google Home, and Home Assistant

What to know before buying:

• At $229, it's the most expensive retrofit option in its class
• No Matter support as of mid-2026; August has not confirmed a timeline
• 2.4 GHz only; 5 GHz networks require a 2.4 GHz band to be active
• Retrofit approach means physical security depends on your existing deadbolt grade

Who Should Buy the August Lock Pro 4th Gen

This lock makes sense for renters who can't modify door hardware, homeowners in historic properties with non-standard exterior hardware, and households already using SmartThings or Ring Alarm who want Z-Wave integration without adding another hub. It's the right fit if you need guest access management, want HomeKit, Alexa, and Google Home under one lock, and prefer not to swap out your existing deadbolt assembly.

If you want a keypad or fingerprint reader on the exterior, or if ANSI/BHMA Grade 1 certification matters to you, look at full-replacement options from Schlage or Yale. The August retrofit approach is a deliberate trade-off: flexibility and reversibility in exchange for keeping your current exterior hardware as-is.