Is the windshield film applied on the inside or outside?
4 Answers
The windshield film is applied on the inside. If it were applied on the outside, exposure to wind and rain would reduce its lifespan by at least two-thirds. Additionally, if applied externally, glass fragments from an impact could still injure people, rendering the anti-shatter film ineffective. Car window tinting involves applying a thin film layer to the front and rear windshields, side windows, and sometimes sunroofs. This film is also known as solar film or anti-shatter heat insulation film. The primary functions of window tinting are to block ultraviolet rays, reduce heat transmission, and prevent injuries caused by sudden glass shattering. It also serves to protect personal privacy through the one-way visibility feature of solar films.
I've been running an auto repair shop for over a decade, and windshield film must be applied to the inner side of the glass. If applied to the outside, daily wind and rain can cause wear, and the wipers' back-and-forth motion can scratch the film surface. The inner side is cleaner, making it less prone to bubbling after application, and it also reduces UV damage to the film layer. During installation, the technician will thoroughly clean the inner surface of the glass to ensure there's no dust or lint. Many people think applying film is simple, but it actually requires a high-standard working environment—ideally, it should be done in a dust-free workshop. Additionally, it's important to choose a certified film with a light transmittance of over 70%; otherwise, it could pose safety hazards when driving at night.
Last time I tried applying the film myself and suffered a big loss, so I specifically consulted a professional. The front windshield film must be applied on the inside. The outside is exposed to sun and rain, and the film will turn yellow and wrinkle in less than half a year. Especially in winter when using wipers to clear snow, ice chips can easily scratch the outer film. Although applying it on the inside is more troublesome, requiring the removal of interior panels to clean the glass, it can extend the film's lifespan by two to three years. Remember not to open the windows within 72 hours after application, or the edges may lift. When choosing the film, don’t go for the cheapest option—low-quality films fade easily and have poor heat insulation.
When I first bought the car, I was also confused about this issue. Later, the owner of the tinting shop demonstrated to me: after peeling off the protective layer of the film, the adhesive side faces inward when applied. Because the outer glass has curvature, direct adhesion would leave gaps. Applying it inside ensures complete conformity to the glass curve, providing better sun protection in summer. After applying the film, avoid using ammonia-based cleaners on the glass as they can corrode the film surface. It's best to choose light-colored films for the front windshield; dark films can be very dangerous when driving at night. Regularly check the edges for any peeling and address it promptly to avoid the entire film being ruined.
