Apple has changed the way iPhone and iPad connect to Wi-Fi networks, starting with the updates for iOS 1
How private WiFi addresses work
When an iPhone, iPad, or other Wi-Fi enabled device connects to a Wi-Fi network, it sends a unique media access control (MAC) address. This identifies the device to the network.
Traditionally, the MAC address was set at the hardware level and was the same for the life of the device. Every network you connect to has been given the same MAC address from your device. You can manually change your MAC address on some devices, but few people have done it.
It’s easy to see how this feature can lead to tracking: when you move around a city that connects to different public Wi-Fi access points in cafes, airports and libraries, your device uses the same MAC address to Connect to an organization that operates the Wi-Fi hotspots to keep track of your location movements and network activity over time.
With private Wi-Fi addresses, the iPhone, iPad, and Apple Watch now offer a different MAC address for each Wi-Fi network they are connected to. Each Wi-Fi network you connect to will get a different MAC address from your device. Your Wi-Fi sessions from different Wi-Fi networks can no longer be easily connected.
How private WiFi can cause problems
Most of the time, you won’t notice a problem with private Wi-Fi addresses. This option is activated by default and “only” works. In some cases, this creates problems with certain networks.
For example, someone may have set up a Wi-Fi network to use MAC address filtering so only certain devices can connect. Your organization may ask you to turn off Wi-Fi private addresses in this situation. At home, you may have set up parental controls for every device on your Wi-Fi network. This feature uses MAC addresses to identify devices and apply restrictions.
If you ever have trouble connecting or accessing the Internet over a Wi-Fi network, turning this option off is a good troubleshooting step that can help you fix your problem in some situations.
How to turn off private addresses for a Wi-Fi network
The “Private Address” option is controlled separately for each Wi-Fi network. Turning it off for a network is not recommended unless you need to (or solve a problem).
To find this option, go to Settings> Wi-Fi on your iPhone or iPad. Find the Wi-Fi network that you want to change this option for. It will appear at the top of the screen when you are currently connected to the network. Tap the “i” icon to the right of the name of the Wi-Fi network.
Deactivate the option “Private address” by tapping the switch on the right.
The option “Wi-Fi Address” shows the private MAC address that is used in this particular network, just in case you need it to configure something on a router, for example.
You will be asked to reconnect to the network if you are already connected. Tap “Rejoin” and your iPhone or iPad will reconnect to its normal MAC address.
The process is the same on an Apple Watch: go to Settings> Wi-Fi, tap the name of the network you’ve joined (or, on a network, swipe left and tap the “…” button, if you have not yet established a connection and deactivate the “Private address” slider.