According to FindLaw, auto glass tinting is the process of applying a film to the safety glass of a vehicle that prevents specific levels of light from passing through. Most new vehicles have the windows tinted during the manufacturing process to stop ultraviolet rays, and they are in accordance with federal and state regulations covering tinting. Aftermarket tinting is also done after the car is sold.
Each state regulates the definition of an auto glass tint and how much tinting is allowed on a window. Different forms of window tints include full-window films that adhere directly to the window, shade bands located horizontally along the top of a window and temporary sunscreens that attach in some way to the window's interior.
Legal limits on tinting are generally based on the amount of light allowed through to the car's interior. This is generally applied as a percentage of the light that passes into the car. There can also be limits on the level of reflectivity of a tint, as most states require that tints be see-through from the outside. Many states allow for exceptions to tinting levels for health reasons. Conditions that allow exceptions include sunlight allergy, melanoma, lupus and photosensitivity.