Instant Hotspot: Tethering Always Enabled
You can use Personal Hotspot on your iPhone to provide Internet access to your other devices without additional setup. You’ll need to sign in to iCloud using the same Apple ID as your iPhone. Also, your cellular provider needs to provision your Personal Hotspot.
After traveling for a week, using Personal Hotspot because it was faster than hotel Wi-Fi, I got home and was surprised to find that the Mac offered my iPhone as a Wi-Fi connection. I had been consistently turning off Personal Hotspot when not using it, and in fact it was off. But it turns out that showing the hotspot anyway is not a bug; it’s Instant Hotspot, part of the Continuity feature in Yosemite. If the Mac and iPhone are using the same Apple ID, Personal Hotspot is always available. You only have to turn on Personal Hotspot to share your phone’s connection with other people’s devices.
Presumably it’s worked this way for months, since iOS 8.1, but I didn’t see this because until my trip I was using an older AT&T plan that didn’t include tethering.
I didn’t notice this during the trip—the hotspot was not available when Personal Hotspot was off—because Instant Hotspot requires Bluetooth, which I turn off when traveling. Interestingly, Personal Hotspot can work over both Wi-Fi and USB, so when charging my iPhone from the Mac, the iPhone would show two Personal Hotspot connections from the same Mac. But this direct connection is not considered sufficient proximity for Instant Hotspot if Bluetooth is off.
Update (2015-05-27): I’m not sure what changed, but my Mac no longer shows my iPhone in the Wi-Fi menu unless Personal Hotspot is enabled.
