List Devices on Your LAN with arp -a
The ARP cache on your Mac lists every device it has recently talked to on the local network.
Run `arp -a` to print all known IP-to-MAC address mappings from the local network cache.
01Command
Command
$ arp -a02What it does
Every packet your Mac sends on the LAN first resolves the destination IP to a hardware (MAC) address, and arp -a shows that cache. The result is a de facto list of recent neighbours: routers, printers, phones, and smart devices, each with IP, MAC, and interface. The MAC's vendor prefix (e.g. Apple, Raspberry Pi Trading) helps identify devices — run a quick ping sweep first if you want a fuller inventory.
03Risk
!Warning: The cache expires after a few minutes of inactivity, so arp -a can miss devices that haven't spoken to your Mac recently.
04Undo
✓No undo needed — this command does not change persistent state.
05Sources
- arp — show and modify the ARP cache (macOS)Evidence: Documents -a to display all current ARP entries with hostname, IP and MAC address.
Last verified: 2026-09-17 · Category: Network