Does Shelly work without the internet?

There are two versions of this question and they have different answers. One is "the internet is down but my router is fine", which is the common one. The other is "there is no network at all", which happens in a blackout or a shed with no coverage. Shelly handles both, differently.

The internet is down, the router is up

Nearly everything keeps working, because the logic runs on the device rather than in a data centre.

The physical switch wired to the input still switches the load. The device's own web interface is still there on your local network, and so is its local HTTP and RPC API. MQTT keeps publishing to a broker on your LAN. Home Assistant on the same network keeps full control, which is why the Shelly and Home Assistant combination is popular with people who care about this.

Shelly says it plainly on their own site: no cloud required.

There is no network at all

The relay is still a relay. The wired switch on the wall still turns the load on and off, because that input is hardwired to the output. You lose everything app-shaped, obviously, and you lose the local API too, since nothing can reach the device.

If the Shelly cannot find your Wi-Fi it can fall back to its own access point. Hold the button for about five seconds and it broadcasts a network you can join directly, then reach it at 192.168.33.1 to reconfigure it. That is also how you set one up in a house with no Wi-Fi yet.

What actually stops without internet

Shelly Cloud remote access stops. So does the app when you are away from home, since that path runs through the cloud. Alexa and Google Home voice control stop, because those commands travel to the assistant's servers and back. Firmware updates need to reach Shelly's servers.

None of that touches the switch on the wall.

The one that catches people: the clock

Shelly relays keep time by syncing over the network rather than from a battery-backed clock, and Shelly's own documentation says the weekly schedule needs a working internet connection so the device can synchronise the time.

In practice that means a schedule keeps running through a short internet outage, because the device already knows what time it is. But a power cut with no internet is different: the device comes back up without a valid clock, and time-based actions cannot run correctly until it syncs again. If you are automating something that matters on a timer, a hot water system or a pool pump, do not put it somewhere with unreliable internet and assume the schedule will hold.

What the relay does when the power comes back

There is a setting for this, called Action on power on in the Gen 4 web interface. Turn ON, Turn OFF, Restore last known state, or, on a toggle switch, follow the current state of the switch. Pick it on purpose rather than leaving the default. A light that comes back on at 3am because the power blinked is a small thing that annoys people for years.

Matter and Zigbee change the picture

The Gen 4 models ship with Matter as the default and can be switched to Zigbee with a button sequence. Running one on Zigbee moves control to your Zigbee hub and takes Shelly's cloud out of the loop entirely. Matter still needs a 2.4GHz Wi-Fi network, a Matter hub with internet access, and Bluetooth to commission it in the first place.

Which generation you have decides what is available, and we have written that up separately in Shelly generations.