Auto identifiers are items used to identify a specific vehicle, such as license plates. License plates are the most common auto identifier, consisting of six letters and/or numbers that are unique to each vehicle. They are typically issued by a state or local government and are required to be displayed on the front and back of a vehicle. Other auto identifiers include vehicle identification numbers (VINs), which are unique 17-digit codes assigned to each vehicle, and registration stickers, which are placed on the windshield and indicate when the vehicle's registration expires.