Unknown Device Connected to WiFi? Check It From Your iPhone

Your router app lists a device you don't recognize. No name, just a string of letters and numbers. Is someone using your Wi-Fi, or is it the new smart plug from last week? In this video we find out from the iPhone: what the device is, when it showed up, and what to do about it.

We use DeviceShelf for iPhone on its demo network, a made-up home with a dozen devices. Nothing you see belongs to a real person. On your phone, the same screens show your own network.

The first question is: which device is the new one? A plain list doesn't tell you. Twelve devices look like twelve devices, whether one of them arrived this morning or two years ago.

DeviceShelf remembers every device it has ever seen. When something joins that wasn't there before, it's marked as new, and the sparkle button in the toolbar counts how many are waiting for your answer. Tap it, and the list shows only those. Here there is one.

Tap it again to see everything. In the full list, the newcomer carries a blue new badge, so it stands out even between familiar devices.

Let's open it. The device has no name. That's common: plenty of gadgets never tell the network what they're called. What we do have is a vendor, Espressif, and the address one ninety two dot one sixty eight dot one dot one eighteen.

The vendor comes from the first half of the hardware address. Every manufacturer registers that part, so it's a reliable clue. But read it carefully. Espressif doesn't sell finished products. It makes the small Wi-Fi chips inside smart plugs, light bulbs, sensors and robot vacuums. So the vendor tells you what's inside, not whose product it is.

Scroll down for what the scan found. The device answers on port eighty, so it serves a small web page, and it announces an http service. A tiny web page is exactly what smart plugs and sensors with Espressif chips tend to have, for setup and firmware updates.

If you want to be sure, the Web UI button opens that page in the browser. Most such devices show their brand, model or firmware right there, and the mystery is over in one tap.

Before you suspect a neighbor, go through the usual suspects. Smart-home gadgets with chip-maker names like Espressif, Tuya or Realtek. TVs, speakers and streaming sticks that woke up. A guest's phone. And very often, your own phone: iPhones and Android phones use a private Wi-Fi address, a made-up hardware address per network, and some change it from time to time. Then the same phone looks like a stranger.

Timing helps too. If the device appeared right after you unpacked something, or right when a visitor arrived, that's your answer. If it shows up at three in the morning and nobody in the house can explain it, that's worth a closer look.

Now decide. The card at the top of the device gives you three choices.

Yes, it's mine, if you recognize it. Ignore, if it's something you don't care about, like a neighbor's printer that a shared network happens to show. And Open router, if you want it gone. DeviceShelf doesn't block devices itself. Blocking is your router's job, and that button takes you straight to its page.

We just set up a smart plug in the kitchen, so this one is ours. Yes, it's mine. The badge goes away, and so does the counter in the toolbar.

While we're here, give it a proper name, so you never have to work this out again. Kitchen smart plug. The name stays with the device, through every future scan.

If you blocked a device in the router and changed the Wi-Fi password, it won't come back. If it does, the new badge will tell you.

So how do you notice the next newcomer? On the phone, the Network Monitor in the settings watches the network while the app is open, and tells you when a device joins or leaves. That's good for a quick check, for example while you switch devices off one by one to see which one disappears.

For a watch around the clock, an iPhone isn't the right tool. Apple doesn't keep an app running in the background long enough to scan. That's what the DeviceShelf server is for: it runs on a NAS, a Raspberry Pi or any always-on computer, scans every few minutes, and sends a push message to your phone when an unknown device joins.

To sum up: let the new badge point you to the device. Read the vendor, but remember that chip makers aren't brands. Look at its ports and open its web page. Then decide: mine, ignore, or block it in the router. And give it a name, so the next unknown device really is unknown. DeviceShelf for iPhone is in the App Store, and the link is in the description.