The names Android Auto and Android Automotive suggest they are variations of the same product. They are not.
Android Auto is the system most drivers have encountered. It works by connecting an Android phone to a compatible car display and projecting a driving-friendly interface onto that screen. The phone does the computing, and the car screen serves as a larger, less distracting place to interact with navigation, music, messaging, and supported apps. As Engadget reported, Android Auto can be used over a USB connection or wirelessly, depending on the phone and vehicle.
Because Android Auto depends on the phone, it travels with the driver. Connecting to a different compatible vehicle brings the same apps, accounts, and preferences along. The car itself may be running any operating system. Android Auto is not a replacement for the car's built-in software but an interface layered on top of it.
Apple's CarPlay works on a similar principle. Even CarPlay Ultra, which extends further into compatible vehicles and surfaces some vehicle controls, still requires an iPhone to function.
Android Automotive OS is a different system entirely. It is installed directly on the vehicle's hardware and operates without any phone connection. Automakers use it to integrate software with infotainment systems, instrument displays, climate controls, electric vehicle information, and other vehicle functions.
Android Automotive OS is open source. Google built-in, which is a separate and optional package, adds licensed Google services on top of it, including native Google Maps, Google Play, and Google's voice assistant, all functioning without a phone. Automakers are not required to include Google built-in even if they build on Android Automotive OS.
Rivian is one example. The company builds its own software experience on top of Android Automotive OS and does not offer Android Auto or Apple CarPlay projection at all.
Polestar illustrates the flexibility on the other end. Its Android Automotive OS-based vehicles can include Google built-in while remaining compatible with Android Auto as well.
The distinction matters when reading a vehicle's spec sheet. A car listed as running Android Automotive OS may or may not include Google built-in, and it may or may not support Android Auto projection. Each of those is a separate feature with a separate specification.
