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How iOS decides which wireless network to auto-join

Source: http://support.apple.com/kb/HT5965

iOS follows these guidelines when deciding which wireless network to auto-join.

iOS defines two categories of networks: hotspot and private.

• A hotspot network can be an HS2.0/Passpoint (802.11u) network, a "captive" network, or an EAP-SIM network. iOS distinguishes between captive / EAP-SIM and HS2.0/Passpoint hotspots.
• A private network is any network that is not a hotspot.

When iOS evaluates SSIDs to auto-join, it prefers known networks, higher levels of security, and stronger relative signal strength (RSSI).

iOS will try to connect to networks in this order:

1. The private network it has most recently previously joined
2. Connect to a private network
3. Connect to a hotspot network

If iOS finds more than one network, it will evaluate SSIDs by security level and choose one based on the following order:

1. Private network: EAP
2. Private network: WPA
3. Private network: WEP
4. Private network: Unsecure/open
5. Hotspot network: HS2.0/Passpoint
6. Hotspot network: EAP
7. Hotspot network: WPA
8. Hotspot network: WEP
9. Hotspot network: Unsecure/open

If iOS finds multiple networks of identical type and security level, it will choose the SSID with the stronger RSSI.

Auto-joining after a restart

After a restart, iOS Wi-Fi credentials are available only after a device is unlocked.

If an iOS 6 device is restarted near both open and secure networks, the device will auto-join the open network because the secure network credentials are not available until the device is unlocked.

After restarting, iOS 7 will not auto-join an open network first because it waits until after the device is unlocked.

Last Modified: Nov 20, 2013

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