Alexa and smart locks: why it will lock but not unlock

An Echo in the hallway and a new deadbolt on the door, and the first thing nearly everyone tries is asking Alexa to unlock the front door. Alexa declines. Locking the same door works on the first attempt, which makes the refusal look like a broken integration or a lock that never linked properly.

It is neither. The asymmetry is deliberate, and the fix takes about two minutes in the Alexa app. What that fix will not do is turn voice into a dependable way of getting through your own front door, which is worth knowing before you plan the household around it.

Why locking is free and unlocking is not

Amazon treats the two commands as different risks, and the logic holds up. Locking a door that is already locked costs nothing and locking one that was open makes the house harder to enter, so there is no reason to verify who asked. Unlocking creates an opening, and a spoken command can be issued by anyone within earshot. Earshot includes a mail slot, a screen door on a summer evening and the far side of a thin apartment wall.

So Alexa accepts “lock the front door” from any voice with no verification at all. Unlocking requires a four digit voice code, set per lock, before the motor will move. Amazon documents this as a fixed behaviour rather than a preference, so there is no setting that removes the prompt while leaving voice unlocking switched on. Several lock makers go a step further and never expose the unlock command to Alexa in the first place.

Setting the voice code

The setting lives in the Alexa app, not in the lock manufacturer’s app, which is where most people look first and give up. Menu wording shifts between app versions, but the sequence has been stable for years.

1. Open the Alexa app, go to Devices, then Locks, then tap the lock itself.
2. Open that lock’s settings from the gear icon.
3. Find the unlock by voice option and turn it on. If it is not there at all, the lock or its skill does not support voice unlocking, and nothing else in the app will add it.
4. Choose a four digit code and confirm it. This code belongs to Alexa and has nothing to do with the codes programmed into the keypad.
5. Test it at the door. Ask Alexa to unlock the door, wait for the prompt, say the four digits, and listen for the bolt.

Two things about that number. Make it different from any code you have programmed into the lock’s keypad, because you will be saying it out loud in a hallway with the door a few feet away. And because it is set on the lock’s own entry in the app, a house with two connected doors can carry a different code on each, which is more useful for a rented basement or a garage entry than it sounds.

Which locks let Alexa unlock at all

“Works with Alexa” on a box is three separate capabilities stacked into one phrase: the lock shows up in the Alexa app, Alexa can lock it, and Alexa can unlock it with a code. Plenty of models do the first two and stop there, and that is a decision made by the lock maker rather than by Amazon.

The reliable source is the manufacturer’s own support documentation, which usually lists the supported commands explicitly, and the skill description in the Alexa app, which normally names them too. If a spec sheet says the lock works with Alexa and nothing else, assume locking and status reporting only until the documentation says otherwise. The habit of checking a specific model against a specific assistant before buying, rather than trusting the badge on the carton, is the same one described in our guide to smart locks and Google Home, and it saves the same disappointment.

Getting Alexa to see the lock in the first place

Before any of this, the lock has to be reachable, and how it becomes reachable depends on the radio inside it.

• Wi-Fi in the lock body. Nothing extra to buy, and linking the account is the whole job.
• Bluetooth only. Needs the manufacturer’s plug-in bridge. Bluetooth reaches your phone at the door, not the house, so without the bridge no assistant will ever see the lock.
• Z-Wave. Needs a hub that has its own Alexa integration; the lock talks to the hub and the hub talks to Amazon.
• Zigbee. Some Echo models include a Zigbee radio and can act as the hub themselves, but which ones do has changed between generations, so check the spec sheet for the exact model on your shelf.
• Matter over Thread. Pairs directly, provided something in the house is acting as a Thread border router.

Matter deserves a caution here, because it looks like it settles the question and does not. The standard covers locking, unlocking and state reporting. It does not cover keypad code management, fingerprint enrollment, auto-lock timers or scheduled guest access, all of which stay inside the manufacturer’s app whichever assistant you use. Our piece on what the Matter badge actually guarantees sets out where that line falls.

What Alexa can tell you about the door

Asking whether the front door is locked works on any lock that reports its state, and this is the part of the integration that earns its keep at bedtime. Read the answer carefully though. A lock without a separate bolt sensor knows what it last did, not what the door is currently doing, so a bolt that was thrown into thin air because the door was standing open will still be reported as locked.

Routines will lock a door on a schedule, at sunset, or as part of a goodnight phrase. The routine builder does not offer unlocking as an action, so any arrangement where the door opens by itself as you arrive has to come from the lock’s own geofencing rather than from Alexa. Amazon’s Hunches feature sits alongside this and can notice an unlocked door late in the evening, either asking whether to lock it or, if you allow it, simply doing so.

Where voice is the wrong tool

Voice is the least dependable route to your own door. It needs the lock online, the internet up, Amazon’s servers answering and the room quiet enough to be understood. Any one of those failing puts you back on the keypad, which is why the keypad code and the physical key still matter on a lock you plan to talk to.

The spoken code is the other limitation. Everyone in the room hears it, including the children who will repeat it, and an Echo placed within a few feet of a glazed door or a single-glazed window can hear a raised voice from outside. The four digit prompt is the only thing standing between that and an open door, which is a reasonable argument against choosing 1234 and against turning voice unlocking on for a door you rarely use. If you want the realistic list of what does and does not threaten a connected lock, we sorted it in can a smart lock be hacked.

Where voice does work well is hands full. A grocery run, a dog on a lead, an armful of laundry heading to the garage, and locking up behind yourself without setting anything down. That command needs no code and no fumbling, and it is the half of this feature most owners end up using daily.

Common questions

Why will Alexa lock my door but not unlock it?

Because unlocking by voice is switched off until you set a four digit code for that lock in the Alexa app. If the option to set one does not appear in the lock’s settings, the manufacturer has chosen not to expose unlocking through Alexa at all, and no amount of relinking the skill will change that.

Can I turn the voice code off?

You can turn voice unlocking off entirely, and you can change the code whenever you like. What you cannot do is keep voice unlocking while removing the prompt. Locking by voice stays available either way and never asks for anything.

Does any of this work when the internet is down?

No. Alexa commands travel to Amazon and back, so an outage at the router, the modem or the service takes the whole voice path with it. The keypad, the app over Bluetooth at close range and the key all keep working, since none of them depends on the connection.

Can Alexa let a guest in while I am out?

Not by voice, since the command has to be spoken to a device in your house by someone who knows the code. Remote access for a visitor is a job for a scheduled keypad code or a remote unlock from the lock’s own app, both of which leave a record of who came in and when.

Do Apple and Google handle this the same way?

Broadly, though the details differ. Every major assistant treats unlocking as the sensitive direction and gates it somehow, whether by a spoken code, a phone that is already unlocked in your hand, or a tap with a watch. Apple’s approach and its Home Key tap-to-enter feature are covered in our guide to HomeKit smart locks.

The short version

Alexa locks a door for anyone who asks and unlocks it only after a four digit voice code, which you set on that lock’s page in the Alexa app rather than in the lock manufacturer’s app. If the option is missing, that model does not offer voice unlocking and never will. Check the radio too, because a Bluetooth-only lock needs a bridge before any assistant can see it and a Z-Wave one needs a hub. Treat the locking command as the useful half of the feature and the unlocking as a convenience that stops working the moment your internet does.