Sooner or later everyone with their own Wi-Fi asks the same question: would I actually notice if a stranger joined? For most people the honest answer is no. The router's device list gets looked at once a year. A notification at the moment a device joins fixes exactly that. Here's how to set one up, with what your router already has or with a scanner.
What routers offer out of the box
Some routers ship with this. AVM's FRITZ!Box can send a push email when a new device logs in (Internet → Push Service → Wi-Fi). UniFi controllers flag new clients in the app once you enable the notification. Many other consumer routers simply have nothing of the sort — then it's the device list, checked by hand.
The router route has two limits. First, it only reports Wi-Fi logins at that router: anything joining over Ethernet, a second access point or a mesh node may not show up at all, depending on the model. Second, it only tells you that something new arrived — not what it is.
The problem with randomized MAC addresses
Before you set up alerts, one expectation to calibrate: modern phones use a randomized MAC address per Wi-Fi network by default, and iPhones can even rotate it periodically in networks they don't trust. For detection this means the same device can come back as a "new device", even though it's your own tablet.
Every solution has to live with that, router or scanner. Two things help in practice: turn off the private address for your home network on your own devices (configurable per network on the iPhone), and limit alerts to unknown devices rather than every new MAC.
Alerts with a network scanner
A scanner with monitoring watches the whole network instead of just Wi-Fi logins: it also sees wired devices, second access points and everything behind mesh nodes, and it identifies the newcomer right away (vendor, type, open ports, name).
With DeviceShelf it works like this: the desktop app monitors the network while your computer is on and raises a notification for new or returning devices. If you want no gaps, run the server edition on a Raspberry Pi, NAS or mini PC around the clock. It sends alerts over email, ntfy, Gotify or webhooks, even with every computer asleep.
For the devices you own, you mark everything as "belongs here" once; from then on, only genuine strangers make noise.
Alerts that don't wear you down
The biggest risk in this setup isn't technical, it's fatigue: get a message for every event and you'll ignore all of them within two weeks. A few rules that hold up:
- Alert on joins, not on every come and go. Your phone leaving the Wi-Fi at night is not news.
- Batch into a digest when several events pile up. Otherwise one access point reboot fills your inbox.
- Mute known devices. The robot vacuum may reappear daily without a beep.
DeviceShelf does this by batching events into a digest and routing by severity: an unknown device is a different message than a known one that was briefly offline.
The short version
- Enable router push if yours has it (FRITZ!Box: Push Service). Better than nothing.
- For real coverage, use a scanner with monitoring that also sees wired and mesh devices.
- Plan for randomized MACs: private addresses off at home, alerts limited to unknowns.
- Set up digests and muting so the one message that matters doesn't drown.