States law determines how license plates must be mounted. The law may specifically say you can’t place the plate on your windshield. However, the plates must be securely fastened, so they don't swing. They must be clear, visible, upright, and the required number of feet off the ground. That means the windshield likely isn’t a legal location for your plate. If an officer pulls you over, you may get a fix-it ticket requiring you to mount your license plate correctly to the bumper or grill. Besides that, a license plate on your windshield can cause serious harm if you're ever in an accident. It’s made of sharp metal and can become a projectile, harming you or your passengers.