

If you’re looking for the fastest and most power efficient tethering option, then USB is the best option. So the best option depends on your needs and personal preference. It is almost 10 times slower than the Wi-Fi tethering.
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The biggest drawback of the Bluetooth option is its limited throughput.

You can only connect to one device at a time with Bluetooth tethering.Bluetooth remains dormant and ready to connect when your device wakes up or is in the range, so you don’t have to take out your iPhone from the pocket to connect like you may need to do with Wi-Fi tethering.Once you connect using the Bluetooth hotspot feature, you won’t get disconnected unless you go out of range.So you will have to disable and reenable Personal Hotspot toggle to connect if you don’t connect your device in time. To minimize power consumption, you get approximately 90 seconds to connect your device to your iPhone using Wi-Fi Personal hotspot feature.This means that you need to connect to your iPhone every time your device gets disconnected. It also seems to be most unstable option, and tends to disconnect. Wi-Fi hotspot turns off when no devices are connected.Wi-Fi tethering consumes the most battery.Wi-Fi tethering also offers the best range.Unlike USB tethering, you can connect more than one device using Wi-Fi tethering. The maximum number of supported connections may vary depending on your carrier.Wi-Fi tethering is not as fast as USB tethering but it is almost 10 times faster than Bluetooth tethering.You can only tether one device at a time.So unlike the wireless options, you won’t be able to tether your iPad to your iPhone etc, which seems to be a popular use case. You can use USB tethering with your computer.It is also the most reliable and stable method.

But note that it will drain your Mac or PC’s battery. You don’t have to worry about your iPhone’s battery life, as your iPhone will be charging when it is being used as a wireless modem.
