Why isn't it possible to set a custom name to a found device?

Custom names are assigned to the MAC address of a device. The name has to be tied to something that uniquely identifies the device, and it cannot be the IP address, because IP addresses can change over time due to DHCP. If the MAC address of a device isn't available, it isn't possible to assign a custom name to it, and the custom name field shows N/A.

On iOS 27 and later, MAC addresses of the found devices are available, so a custom name can be assigned to any of them. Tap the Custom Name row on the device's details page — it opens the MAC Browser, where both a custom name and a custom vendor can be entered for the device's MAC address. The name is then shown everywhere in the app where the device appears, and it is kept across scans and networks. The only device without a MAC address is the phone running the scan itself; its name is edited directly in the Custom Name row.

On iOS 11 to iOS 26, the app cannot access MAC addresses, so custom names cannot be assigned to devices. As a workaround, the Assign Name to IP row on the device's details page lets you assign a name (and optionally the MAC address and vendor) to the device's IP address instead. Use this only when you are absolutely sure that the IP address of the device cannot change; otherwise, the name will end up on a wrong device. Names assigned to IP addresses are valid for the current history item only and are cleared when the scan is deleted from the history.