iOS defines two categories of networks: hotspot and private.
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- 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 isn't a hotspot. iOS considers its own ‘Personal Hotspot’ a private WPA network. 

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:
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- The private network it most recently joined 
	
- A private network 
	
- A hotspot network 

If iOS finds more than one network, it evaluates SSIDs by security level and chooses one based on the following order:
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- Private network: EAP 
	
- Private network: WPA 
	
- Private network: WEP 
	
- Private network: Unsecure/open 
	
- Hotspot network: HS2.0/Passpoint 
	
- Hotspot network: EAP 
	
- Hotspot network: WPA 
	
- Hotspot network: WEP 
	
- Hotspot network: Unsecure/open 

If iOS finds multiple networks of identical type and security level, it chooses the SSID with the strongest RSSI.
Auto-joining after a restart
After a restart, iOS Wi-Fi credentials are available only after you unlock your device.
On iOS 7 and earlier, if a device is restarted near both open and secure networks, the device auto-joins the open network because secure network credentials aren't available until the device is unlocked.
After a restart on iOS 7 and later, the iOS won't auto-join an open network first because it waits until after the device is unlocked.