Car window film is a thin, multi-layered laminate sheet that is applied to the interior of a vehicle's windows. It's made primarily of polyester and treated with various coatings and adhesives to achieve different functions.

People install window film for several important reasons:
Heat Rejection & UV Protection: This is a primary reason, especially in sunny climates. High-quality films can block a significant amount of infrared radiation, keeping your car cooler, reducing AC load, and improving fuel efficiency. They also block 99% of harmful UV rays, which protects your skin and prevents the interior (dash, seats) from fading and cracking.
Glare Reduction: Reduces eye strain from the sun and headlights, making driving safer and more comfortable.
Privacy and Security: Darker tints prevent outsiders from easily seeing into your vehicle, which can deter theft of valuables left in the car.
Safety and Shatter Resistance: The film acts as a bonding agent, holding shattered glass together in the event of an accident or break-in. This prevents glass shards from causing injury and can make it harder for someone to break in.
Aesthetic Appeal: A well-tinted car often looks more stylish and sleek.