Why does Carplay need wifi turned on, even though my vehicle is not signed into any wifi network?

Idkydu wrote:

Then why does it create a wi fi network that I have to connect to in order to use CarPlay?

Because your iPhone needs to communicate with your infotainment system (somehow), and that connection can happen through various means including ad-hoc or infrastructure Wi-Fi, or Bluetooth, or cable, or otherwise, with details here depending on the particular infotainment system.

Some cars have a built-in Wi-Fi network, as well.

Subaru offers some vehicles with that built-in Wi-Fi option, and is offering STARLINK in some models, which uses satellite communications to connect to the internet. They’re probably offering cellular connections with other configurations; those with Wi-Fi but without STARLINK. This all for communications with services outside your vehicle. CarPlay stays in your car, except for what the iPhone streams from music or other services.

For the details of your particular Subaru and of your particular infotainment system and any built-in features, check with your dealer.

This reply will probably read like technobabble, of course. 😉 I’m not sure if a Today at Apple (free) class or two at a local Apple Store might help, and might provide a place to ask questions, or some other way to learn about this stuff, if you’re inclined to invest some time. If not, the most direct path is probably to ask the dealer for help getting CarPlay going.

Use CarPlay with your iPhone - Apple Support

"If your car supports only wireless CarPlay, press and hold the voice command button on your steering wheel. Make sure that your stereo is in wireless or Bluetooth mode. Then on your iPhone, go to Settings > Wi-Fi, and make sure that Wi-Fi is also turned on."

It sounds to me quite possible that CarPlay does use Wi-Fi under some circumstances. I'm not sure whether that would involve one device acting as an access point and the other as a client, or if the car stereo and iPhone would act as peer-to-peer devices in an "ad hoc" Wi-Fi network. Home Wi-Fi "routers" and public Wi-Fi hotspots always use the "access point" / "station" mode of operation, but the "ad hoc" mode is part of standards, too.

In either case, the Wi-Fi network would consist of the car and the iPhone. You wouldn't be connecting (by choice, anyway) to Wi-Fi networks in other vehicles or in a building. If you were parked. say, in your garage at home – so close you were within range of your Wi-Fi router – you might find that you had to disengage any wireless CarPlay mode before you could make a connection to your home Wi-Fi Internet service.

CarPlay does not use WiFi, it uses Bluetooth or a wired connection to a USB port in your car. In addition your vehicle must support CarPlay to begin with. Check with your dealer or look in your car’s user manual.

Then why does it create a wi fi network that I have to connect to in order to use CarPlay?