UV films have inhibitors in the adhesive that filter out 99% of UV rays from the sun. UV films can be clear, tinted, or frosted. UV is the main factor that causes fading. Heat, and light contribute as well. UV films are recommended protection by the Skin Cancer Foundation.
Here you can see the damage done to a hardwood floor from the sun. Over time, the exposed wood has faded and turned to a lighter colour compared to the wood that was covered up under the floor mat.