What is the reason for utilizing randomized hardware addresses?

Devices use randomized hardware addresses because a Wi-Fi interface that always presents the same address is a stable identifier: a network, or any observer in radio range, can recognise the same device the next time it appears. Randomizing the address per network removes that one identifier. Apple enables it by default from iOS 14 and iPadOS 14, Android from version 10, and Windows 10 and 11 offer it as a switch you turn on.

What leaks an identity before a device even joins

A Wi-Fi device that is not connected still transmits frames to find networks: probe requests, and in some cases association requests to a network it already knows. Those frames carry an address, so a device can be recognised while it is merely switched on and within range. Microsoft documents this behaviour for Windows: while the device is offline, the signal it broadcasts to search for nearby networks includes its physical MAC address, which is why the setting there covers scanning as well as connecting. Apple randomizes the address of peer-to-peer interfaces such as AirDrop, AirPlay and Personal Hotspot, and presents a private address on each Wi-Fi network it joins.

What randomization protects, and what it does not

• It protects against cross-network linking. The address a café sees is not the address your home router sees, so records collected in two places cannot be joined by that field alone.
• It does not hide the traffic. The network you join still carries your traffic and can log what it sees at its own layer.
• It does not make the device anonymous. Other signals — the set of networks a device remembers, timing, or the identifier of a paired account — can still correlate it. Treat randomization as one measure that raises the cost of tracking, not as a guarantee.
• It can conflict with legitimate filters. Networks that register, meter or bill devices by address, and captive portals that remember a device, need a stable address. Apple's Fixed mode and Android's persistent randomization exist for that case.

How to turn it on

• iPhone, iPad, Apple Watch, Mac and Apple Vision Pro: see private Wi-Fi addresses on Apple devices. It is on by default; the choice is Off, Fixed or Rotating, per network.
• Android: Settings > Network & internet > Wi-Fi , tap the gear icon next to the network, then open Privacy . See randomization on Android.
• Windows 10 and 11: Settings > Network & internet > Wi-Fi , then turn on Random hardware addresses for all networks or for one network. See random hardware addresses on Windows.
• Linux: NetworkManager randomizes the address while scanning by default and can assign one per connection. See randomization on Linux.

Why a lookup returns no vendor

A randomized address is locally administered: the second-least-significant bit of its first octet is 1, so the second hexadecimal digit is 2, 6, A or E. No IEEE registration covers it, so a lookup returns no registered organization. The same answer appears for every randomized address on every platform.