Best Retrofit Smart Locks for Existing Deadbolts
A retrofit smart lock replaces only the interior half of your existing deadbolt, so you keep your current keys, exterior hardware, and door prep. That makes them a strong fit for renters, apartment dwellers, and anyone who does not want to swap out a full lockset or drill new holes.
Quick answer
The August Wi-Fi Smart Lock (4th Gen) is the best overall retrofit pick for most existing single-cylinder deadbolts because it keeps your outside keyway and adds app, auto-unlock, and voice control.
Why trust ToolBuyerHub
- Cross-checked manufacturer-published specifications before writing any recommendation
- Verified US market availability and configuration for every model discussed
- Owner-feedback themes are summarized as feedback, never presented as our own hands-on testing
- No invented star ratings; see the visible Research Score criteria on this page
- Checked specifications against manufacturer documentation before publishing
- We compare retrofit locks by deadbolt compatibility, whether a hub or bridge is required for remote access, and how the interior assembly fits around existing thumbturns.
Research updated September 2026.
What Matters Most for This Category
The single biggest factor is compatibility with your existing deadbolt. Retrofit locks generally work with standard single-cylinder deadbolts that have a removable interior thumbturn, but they do not work with double-cylinder deadbolts, most mortise locks, or integrated handle-and-lock combos. After fit, decide whether you want Wi-Fi built in or are fine adding a bridge, whether you need Apple Home or Matter support, and whether you care about keeping a physical key on the outside. Battery type and how often you must recharge also matter more than most buyers expect.
| Model | Best for | Key specs | Research Score |
|---|---|---|---|
| August Wi-Fi Smart Lock (4th Gen) | Best Overall | Retrofit interior assembly, Built-in Wi-Fi, Bluetooth | 93/100 |
| Level Lock+ (Apple HomeKit) | Best Premium | Full deadbolt with hidden smart tech, Bluetooth, Apple HomeKit | 90/100 |
| Yale Approach Lock with Wi-Fi | Best for Renters | Retrofit interior assembly, Built-in Wi-Fi, Bluetooth | 88/100 |
| August Smart Lock Pro (3rd Gen) | Best for Apple Home | Retrofit interior assembly, Bluetooth, Z-Wave Plus, HomeKit | 87/100 |
| Wyze Lock Bolt | Best Budget | Full deadbolt replacement, Bluetooth | 84/100 |
| Schlage Encode Plus Smart WiFi Deadbolt | Best Full Replacement Alternative | Full deadbolt replacement, Built-in Wi-Fi, Bluetooth | 86/100 |
| Kwikset Halo Wi-Fi Smart Lock | Best for Simple Wi-Fi Setup | Full deadbolt replacement, Built-in Wi-Fi | 83/100 |
August Wi-Fi Smart Lock (4th Gen)
Top PickPros
- Keeps your existing exterior key and hardware
- Built-in Wi-Fi means no separate bridge for remote access
- Auto-unlock and door-sense features work well for hands-free entry
Cons
- Bulky interior unit can crowd some door frames
- Battery life varies a lot with Wi-Fi use
August's fourth-generation lock is the most recognized retrofit option and mounts over your existing deadbolt's interior side. It adds app control, auto-unlock, and voice assistant support without changing your keys. Based on manufacturer specifications, it connects directly to Wi-Fi so you do not need an extra hub.
Level Lock+ (Apple HomeKit)
Invisible SmartPros
- Smart electronics are hidden inside the lock body
- Keeps a traditional keyed exterior look
- Supports Apple HomeKit and home keys
Cons
- Replaces the whole deadbolt rather than just the interior
- HomeKit-centric, less ideal for Alexa or Google households
Level Lock+ hides all the smart hardware inside the deadbolt itself, so nothing changes visually on either side of the door. It is technically a full replacement rather than a pure retrofit, but it installs in the same standard deadbolt bore and preserves the classic look. Based on manufacturer specifications, it works with Apple HomeKit and supports tap-to-unlock features on compatible iPhones.
Yale Approach Lock with Wi-Fi
Renter FriendlyPros
- Installs over the existing deadbolt interior
- Built-in Wi-Fi avoids a separate bridge
- Works with major voice assistants
Cons
- Interior module is fairly large
- App setup can take a few tries
Yale's Approach retrofit lock attaches to your existing deadbolt and adds Wi-Fi, app control, and keypad-free entry through the app. It is designed to be removed and taken with you when you move, which suits renters. Based on manufacturer specifications, it works with Amazon Alexa, Google Assistant, and other common platforms.
August Smart Lock Pro (3rd Gen)
HomeKit ReadyPros
- Supports Apple HomeKit and Z-Wave
- Keeps your existing exterior key
- DoorSense open/closed detection included
Cons
- Needs the included Connect bridge for remote access
- Older model, so stock and pricing vary
The third-generation August Smart Lock Pro remains a popular retrofit choice for Apple and smart-home hub users. It keeps your existing keyway and adds app control, auto-unlock, and DoorSense. Based on manufacturer specifications, remote access requires the bundled Connect bridge rather than built-in Wi-Fi.
Wyze Lock Bolt
Low CostPros
- Very low price for a smart deadbolt
- Built-in fingerprint reader
- Simple app setup
Cons
- Bluetooth only, no remote access without extra hardware
- Replaces the whole deadbolt rather than retrofitting
Wyze's Lock Bolt is a budget-friendly smart deadbolt with a fingerprint reader and app control. It is a full replacement rather than a pure retrofit, but it fits a standard deadbolt bore and costs far less than most premium options. Based on manufacturer specifications, it connects over Bluetooth, so remote access is limited.
Schlage Encode Plus Smart WiFi Deadbolt
Built To LastPros
- Built-in Wi-Fi with no bridge needed
- Strong residential security brand reputation
- Supports Apple home keys on compatible devices
Cons
- Replaces the entire deadbolt, not a retrofit
- Higher price than most retrofit options
Schlage's Encode Plus is a full deadbolt replacement with built-in Wi-Fi and support for Apple home keys. It is not a retrofit, but it is the go-to alternative when your existing deadbolt is not compatible with retrofit kits. Based on manufacturer specifications, it works with major smart home platforms and uses standard AA batteries.
Kwikset Halo Wi-Fi Smart Lock
Easy InstallPros
- Built-in Wi-Fi with no hub required
- Familiar residential lock brand
- Straightforward app and keypad use
Cons
- Full replacement rather than retrofit
- Fewer advanced automation features than premium rivals
Kwikset's Halo is a Wi-Fi smart deadbolt that installs in a standard bore and connects directly to your network. It is a replacement rather than a retrofit, but it is a reasonable fallback when a retrofit kit will not fit. Based on manufacturer specifications, it offers app control, keypad entry, and voice assistant support.
Who Should Avoid the Top Pick
Skip retrofit locks if you have a double-cylinder deadbolt, a mortise lock, or an integrated handle-and-deadbolt combo, since these usually cannot accept an interior retrofit module. Also avoid them if you rent and your lease forbids any lock modification, or if you need a keypad on the outside, because most retrofit kits keep your original exterior hardware.
Before You Buy
Check your existing deadbolt first. Remove the interior thumbturn and confirm it is a standard single-cylinder deadbolt with a compatible mounting pattern, since most retrofit kits list specific brands and models they support. Measure your door thickness and backset, confirm whether you need built-in Wi-Fi or are fine with a bridge, and decide which smart home platform you use. Finally, check the return policy in case the fit is not right.
FAQs
Do retrofit smart locks work with any deadbolt?
No. They work with many standard single-cylinder deadbolts that have a removable interior thumbturn, but they generally do not fit double-cylinder deadbolts, mortise locks, or integrated handle-and-lock assemblies. Always check the manufacturer's compatibility list before buying.
Can I keep my existing keys with a retrofit smart lock?
Yes, that is the main appeal. A retrofit lock replaces only the interior side, so your exterior keyway and keys stay the same. You gain app control and smart features without changing how you unlock from outside.
Do retrofit smart locks need a hub or bridge?
It depends on the model. Some have built-in Wi-Fi and connect directly to your network, while others use Bluetooth only and need a separate bridge for remote access and integrations. Check the connectivity specs before you buy.
Are retrofit smart locks good for renters?
They can be, because many install without damaging the door and can be removed and taken with you. However, you should still get landlord approval and keep the original interior thumbturn so you can restore the lock when you move out.
How long do the batteries last?
Battery life varies widely by model and usage. Locks with built-in Wi-Fi tend to drain faster than Bluetooth-only models, and heavy auto-unlock use shortens life further. Most use standard AA or similar batteries that you replace rather than recharge.
Can I still use a keypad with a retrofit lock?
Usually not on the outside, because retrofit kits keep your original exterior hardware. If you want a keypad, you generally need a full deadbolt replacement with a keypad built in, or a separate keypad accessory if the manufacturer offers one.
Our verdict
For most people with a standard single-cylinder deadbolt, the August Wi-Fi Smart Lock (4th Gen) is the easiest way to add smart entry while keeping existing keys and hardware. If you want hidden tech and use Apple Home, the Level Lock+ is worth the premium, and renters should lean toward a removable retrofit like the Yale Approach. Confirm compatibility before buying, since fit is the one thing that decides whether any of these will work.