Does your smart home work without internet?

Internet down is not the same as power out

There are two failures. In an internet outage, your router and devices have power and talk to each other, but nothing reaches the outside world. In a power outage, the router, hub and plug-in devices stop unless they are on a battery. This page covers the first. For the second, see the power outage backup kit and the UPS runtime calculator.

What usually keeps working

• Matter devices on your local network. The Connectivity Standards Alliance describes Matter as offering consistent and responsive local connectivity, running over Wi-Fi and Thread with Bluetooth Low Energy for setup. Local control by a Matter controller in your home continues when the internet is down.
• Thread devices. Thread is a low-power IP mesh built on IEEE 802.15.4. The Thread network lives in your house, with a border router linking it to Wi-Fi.
• Zigbee devices with a local hub. The CSA describes Zigbee as a self-healing mesh with low power use. A hub or USB coordinator running local automations keeps sensors and bulbs responding.
• Home Assistant. Its website says it keeps data local, communicates with devices locally and processes everything locally, and falls back to cloud data only when there is no other option. The project’s own blog argues that the cloud should extend the home rather than run it.
• Apple Home with a home hub. A HomePod, HomePod mini or Apple TV acts as the home hub that runs automations and gives remote access. Apple notes that the hub is required for Matter accessories and that Thread accessories need a Thread-capable hub.
• Battery sensors, button and door locks. A keypad lock still works with its code or key.

What usually stops

Many products mix the two: the device is controlled locally, but the account, the routines or the voice integration live in the cloud. Check each product’s documentation for “local control” rather than assuming.

Test your own home in 15 minutes

1. Write the list of automations and devices that matter: locks, lights, thermostat, doorbell, cameras, alarms, voice.
2. Unplug the cable that links the router to the modem, or turn off the modem. Keep the router on so your local network stays up.
3. Wait two minutes, then use each device by app, by voice and by hand.
4. Trigger a sensor automation, such as a door opening turning on a light.
5. Check which devices show offline in the app, and which still respond to physical controls.
6. Restore the connection and note any device that did not reconnect on its own.

Record the result in a note on your phone. The devices that failed are the ones to replace, move to a local protocol or keep a manual fallback for. A smart lock should always have a key or code that works without the app.

How to make your setup more resilient

• Prefer local protocols for the things you rely on: locks, lights, motion sensors, thermostats. See Matter vs Zigbee.
• Choose a controller that runs automations locally: a hub, a Home Assistant box or a home hub that supports your devices.
• Keep physical controls. Wall switches that still work, and a key for the door.
• Record locally. Use cameras that store clips on an SD card or a local recorder.
• Give your router a battery. The internet may still be down, but your local network will not go dark in a power flicker.
• Know your fallback internet. Your phone’s hotspot can keep one device online for essential alerts.

If you want to go further, the local-only smart home kit lists the parts. If devices drop off your network even when the internet is fine, see smart devices that keep going offline.