Get an Alert When a New Device Joins Your WiFi (2026)
Short version. Three approaches work: your router, if it supports notifications; a self-hosted monitor on a device that never sleeps; or an always-on app on a Mac you already leave running. What does not work is a phone app alone, because iOS suspends apps in the background and cannot watch anything while you are not looking at it.
The usual trigger for this search is opening a scanner, seeing a device you do not recognise, and realising you have no idea how long it has been there. A one-off scan cannot answer that. Something has to be watching.
Full disclosure: I build PingKit Agent, so weigh the recommendation accordingly. The limits section is not padding, and there is a whole category of Mac network tool below that PingKit deliberately is not.
Why Your Phone Cannot Do This Alone
Worth understanding before you install anything, because several App Store listings imply otherwise. iOS suspends apps when they are not in the foreground. There is no background mode that lets an app sweep your network on a schedule while your phone is in your pocket.
So an iPhone app can tell you what is on the network right now, while you are looking at it. It cannot notice a device that joined at 2am. Any product promising that is either using a companion device that stays awake, or overstating what it does.
The Three Approaches That Work
1. Your router
Free, already installed, and the most reliable place to see truth because every device has to ask it for an address. Many mesh systems (eero, Google Nest WiFi, Ubiquiti, some ISP routers) can push a notification when an unknown device joins.
Check this first. If your router does it, you are finished, and it will also let you block the device, which no app can do.
The limitation is that most routers show a MAC address and little else, and modern phones randomise their MAC per network, so the list fills with unidentifiable entries over time.
2. Something self-hosted that never sleeps
A Raspberry Pi or NAS running a monitoring tool. Total control, no subscription, and it is a project you now maintain. Good if you enjoy that.
3. An always-on app on a Mac
If you already leave a Mac powered, it can do the watching. That is what PingKit Agent is: a menu bar app that keeps sweeping at an interval you set and raises an alert when something changes.
It has nine alert types: new device, device offline, device online, internet down, internet restored, latency spike, speed below threshold, security risk, and service changed, which fires when a device alters what it advertises. That last one catches a device whose role changed even though it was already on your network.
Alerts also reach your iPhone, because the Agent publishes to your own private iCloud database and the PingKit iPhone app reads from it. The Mac does the watching; the phone is the screen.
Identifying What You Found
An alert saying "new device" is only useful if you can work out what it is. On a Mac, identification uses the real MAC address and vendor prefix from the ARP table, plus Bonjour and SSDP service advertisements, hostnames and open port patterns. A device announcing AirPlay is a speaker or a TV; one advertising IPP is a printer.
Before you panic about an unknown device. Most turn out to be something you own. Modern phones and laptops randomise their MAC address per network, so your own devices can appear unfamiliar. Count your devices first, including anything with WiFi you forgot about: a thermostat, a doorbell, a games console, a printer, a smart plug. The number is almost always higher than people expect.
Honest Limits
- The Mac has to be awake. A sleeping Mac is a paused monitor. If your Mac sleeps overnight, use your router or a device that stays on.
- No app can block a device. That is your router's job.
- Detection is by network sweep, so a device that joins and leaves entirely between two sweeps can be missed. Shorten the interval if that matters.
- Device naming is good, not infallible. Unusual hardware sometimes stays unlabelled.
- Continuous alerting is a Guardian feature, $2.99/month or $24.99/year on the Mac. macOS 15 or later.
Frequently Asked Questions
Can my iPhone alert me when a new device joins my WiFi?
Not on its own. iOS suspends apps in the background, so no iPhone app can sweep your network while your phone is idle. You need something that stays awake: your router, a self-hosted monitor, or an always-on Mac app that sends the alert to your phone.
How do I know if someone is using my WiFi?
Compare the device list against what you own, remembering that phones and laptops randomise their MAC addresses per network, so your own devices can look unfamiliar. Continuous monitoring is more useful than a one-off scan, because it tells you when something appeared rather than only what is there now.
Can my router notify me about new devices?
Many can. Most mesh systems including eero, Google Nest WiFi and Ubiquiti support new device notifications, and some ISP routers do too. Check this first: it is free, it is already running, and your router can also block the device, which no app can do.
What is the 'service changed' alert?
It fires when a device on your network alters the services it advertises, for example starting to offer file sharing or a web interface it was not offering before. It catches a device whose role changed even though it was already connected.
Will I get the alert on my phone?
Yes, if you also use the PingKit iPhone app. The Mac Agent publishes alerts to your own private iCloud database and the iPhone app reads them. The Mac does the monitoring; the phone displays it.
Know the moment something joins
New device alerts plus eight other alert types, running continuously in your menu bar and syncing to your iPhone. macOS 15 or later.
Get PingKit Agent for Mac