To see who's on your Wi-Fi, open your router's admin page and look at its connected-devices list, or run a network scanner that pings every address on your subnet. Each entry shows an IP, a MAC address, and often a hostname. From there you match each device to something you actually own, and whatever's left over is worth a closer look.
Start with your router's device list
Type your router's address into a browser (often 192.168.1.1 or 192.168.0.1, printed on a sticker on the box). Log in, then find a section called Attached Devices, DHCP Clients, or Connected Devices. You get a table of everything the router has handed an address to: IP, MAC, and sometimes a name.
This is the fastest free check, but router lists have limits. They often miss devices on a guest network or a second access point, they drop stale entries slowly, and the names are frequently blank or cryptic.
Read the MAC address and vendor (OUI)
Every network device has a MAC address, six pairs of hex like a4:83:e7:2b:19:0c. The first three pairs are the OUI (Organizationally Unique Identifier), assigned to the manufacturer. a4:83:e7 maps to Apple, for instance. Look the prefix up in any OUI database and an anonymous row becomes "some Apple device."
Vendor alone rarely finishes the job. A house full of Apple gear turns into a wall of "Apple, Apple, Apple," and you still have to work out which entry is the iPhone and which is the Apple TV.
Get real names with hostnames and mDNS
Hostnames close some of that gap. Many devices announce a name over DHCP or mDNS/Bonjour, like Christofs-MacBook or living-room-tv. NetBIOS does the same on older Windows networks. A scanner that queries all three resolves far more names than the router shows on its own.
Why randomized MAC addresses confuse things
Since iOS 14, Android 10, and recent Windows builds, phones use a random MAC per network by default, and some rotate it over time. The upside is privacy. The downside for you is that a phone can show up under a vendor prefix that no longer maps to its maker, and a device you already trust can look brand new after a rotation.
Work around it by matching on hostname and behavior rather than MAC alone, and by naming devices in a tool that remembers them across scans, so a rotated address doesn't reset your whole inventory.
Name everything in one pass with a scanner
Doing all of the above by hand is slow. A scanner sweeps the whole subnet, collects MAC/OUI vendor, hostname, an OS guess, and open ports, then hands you one labeled inventory. nmap does this from the command line (nmap -sn 192.168.1.0/24 for a quick host sweep). GUI tools do the same with less typing.
DeviceShelf is one such scanner. It discovers every device on your LAN or Wi-Fi, identifies each by vendor, hostname, and type, and lets you rename and pin the ones you recognize so the list stays meaningful next time. It runs locally, with no account and no data leaving your machine, which is why people looking for a private alternative to Fing tend to land on it. If you're weighing tools, our comparison of network scanners shows where each one fits.
Spotting a device that isn't yours
Once every entry is named, the unknowns stand out. Go one by one: power a suspect device off and see which row drops, or check the vendor against what you own. A camera vendor you don't recognize, an open Telnet port, or a host that only appears at odd hours all deserve a second look.
Ongoing checks matter more than a one-time audit. New-device alerts tell you when something joins that wasn't there yesterday, which is how you catch a neighbor on your Wi-Fi or a gadget quietly phoning home.
You can do every step here with free tools and some patience. If you'd rather get the labeled list and the alerts in one pass, DeviceShelf has a free 7-day trial, no account needed.