Do Car Windows Offer UV Protection? Windshield vs Side (2025 Study)
Car windows block most UV light, but not all of it. The Skin Cancer Foundation says glass filters most UVB while UVA passes through, and a 2025 study of 34 vehicles measured windshields blocking 99.25% of UVA on average against 88.78% for driver’s side windows. This guide lines up each window, the sunroof and UV film side by side, with the source and year for every number.
Do Car Windows Block UV Rays? The Basics
Partly. Which rays get through depends on the type of ray and the piece of glass. Per the Skin Cancer Foundation, window glass does a good job of filtering most UVB, while UVA has a longer wavelength and passes through windows and clouds year-round. Windshields are laminated glass treated to shield drivers from some UVA; side, back and sunroof glass is usually tempered and does not block UVA effectively.
Best Windshield Sunshade Pick
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Motor Trend Windshield Sunshade, Black Accordion Fold, 58 x 24 Inch Best for: Putting a physical cover over the windshield while the car is parked. Why we picked it: The listing describes a 58 by 24 inch accordion shade with a dual-layer design that sits against the glass, is held up by the rearview mirror, reverses to either side and closes with a hook-and-loop strap. Main drawback: It covers only the windshield and only while parked, so it does not shield you from the side windows while you drive. Treat the listing’s own UV claims as the seller’s, not as measured results. |
As an Amazon Associate we earn from qualifying purchases. Spec-based pick from the listing, not a hands-on test.
| Glass | What the source says about UV | Source |
|---|---|---|
| Windshield (laminated) | Mean UVA reduction 99.25% across 34 vehicles, lowest single reading 91.67%; UVB reduction 100% | Axelson et al., Archives of Dermatological Research, 2025 |
| Driver and passenger side windows | Mean UVA reduction 88.78% (driver) and 88.99% (passenger); lowest single reading 65.22% | Axelson et al., 2025 |
| Rear side windows and back glass | Mean UVA reduction 93.18% and 95.57% (rear left and right) and 95.36% (back) | Axelson et al., 2025 |
| Sunroof | Sunroof glass is usually tempered and does not block UVA effectively | Skin Cancer Foundation, 2024 |
| UV window film on glass | Can block more than 99% of UVA and UVB; one maker says up to 99% | Skin Cancer Foundation, 2024; LLumar FAQ |
What UV Protection Does and Does Not Mean
The label sounds absolute, but the sources describe a sliding scale. Here is how to read it.
- Does mean: glass filters most UVB, the ray mainly tied to sunburn (Skin Cancer Foundation).
- Does mean: a windshield is built to cut UVA too, and in the 2025 study it did so for 99.25% on average.
- Does not mean: that UVA is blocked everywhere. The Skin Cancer Foundation says UVA passes through window glass and reaches you on the road.
- Does not mean: that every window on one car performs alike. The same study found the driver’s and passenger side windows lagged the windshield in most vehicle groups.
- Does not mean: that a darker window is a safer one. The foundation notes that many films are made only for design or darkening.
What Are UV Ray Transmission Rates?
A transmission rate is the share of UV that gets through the glass; a reduction rate is the share stopped. The study by Axelson and colleagues in Archives of Dermatological Research (2025) measured UVA and UVB reduction on 34 vehicles of model years 2015 to 2025 at dealerships in Philadelphia and New York City in June and July 2024, using SolarMeter handheld UV meters. The table shows mean UVA reduction by window. Higher means more UVA blocked.
| Vehicles (n) | Front | Driver’s | Passenger | Rear left | Rear right | Back |
|---|---|---|---|---|---|---|
| All (34) | 99.25% | 88.78% | 88.99% | 93.18% | 95.57% | 95.36% |
| Gas (15) | 98.62% | 89.22% | 90.51% | 97.06% | 98.27% | 98.01% |
| Hybrid (9) | 99.74% | 86.86% | 86.08% | 89.56% | 92.89% | 92.47% |
| Electric (10) | 99.84% | 88.82% | 92.03% | 90.85% | 92.58% | 95.85% |
UVB was a non-issue in that data: every window blocked 100% of UVB except one rear left window on a 2024 Honda CR-V, which read 37.5% and stayed an outlier on repeat measurement. UVA is where the spread shows up, with readings across all windows from 65.22% to 100%.
Which Vehicles Protect Better
The authors split the results by vehicle type. Driver’s side UVA reduction averaged the following, with n the number of vehicles tested.
| Vehicle group | Driver’s side mean UVA reduction |
|---|---|
| Luxury (7) | 94.68% |
| Trucks (7) | 93.85% |
| Gas (15) | 89.22% |
| Electric (10) | 88.82% |
| SUVs (20) | 88% |
| Non-luxury (27) | 87.25% |
| Hybrid (9) | 86.86% |
| Sedans (6) | 85.97% |
For trucks and luxury vehicles the authors found no significant difference between the windshield and the other windows, while SUVs and non-luxury vehicles did differ significantly. The authors also cite a 2014 study (Boxer Wachler) that measured an average of 71% UVA protection at side windows, so 88.78% is an improvement, though not a complete one.
A Second Data Set: Broadband UV Readings
A Frontiers in Public Health study (AlQahtani et al., 2025) used a different method: a radiometer on 20 unshaded vehicles in Dammam, Saudi Arabia, in June 2021. Mean UV outside was 3.92 mW/cm2. Behind the front window the mean was 0.32 and behind the side window 0.82 (maximum 0.80 and 1.70). By my arithmetic from those means, the front glass passed about 8% and the side glass about 21%. The two studies use different methods, so compare direction, not numbers.
Factors Affecting UV Protection
- Glass type: laminated glass has a PVB plastic layer between panes that reduces UV; tempered glass has none (AlQahtani et al.).
- Colour and thickness: the 2025 authors say these influence UV transmission but could not confirm either by looking at the glass.
- Mileage: in their regression, more miles went with higher driver’s side UVA reduction (p = 0.013), while model year did not predict it.
Understanding UV Rays and Your Skin
The Skin Cancer Foundation describes UV radiation as a proven human carcinogen and says damage is cumulative: the body repairs some DNA damage in skin cells but not all of it. It calls UVB the ray mainly tied to sunburn and UVA the ray that penetrates more deeply and drives tanning and skin aging, and says both contribute to skin cancer risk. The CDC says most skin cancers are caused by too much exposure to UV rays.
Why the Driver’s Side Gets Singled Out
The foundation cites a New England Journal of Medicine case of a 69-year-old man who drove a delivery truck for 28 years, with visibly more sun damage on the left side of his face, and says melanoma and nonmelanoma skin cancers are more common on the left side in the U.S. The 2025 Archives of Dermatological Research paper adds that an Australian study, where cars drive on the other side of the road, found more skin cancer on the right side of the face. These are patterns across groups of people, not predictions for any one driver.
For a specific mole or spot you are worried about, see a dermatologist. For everyday habits the agencies point the same way: the FDA lists limiting time in the sun from 10 a.m. to 2 p.m., covering skin with clothing, and using broad spectrum sunscreen of SPF 15 or higher; the CDC says to protect your skin when the UV Index is 3 or higher.
Understanding Window Tinting and UV Protection
Tint is the one upgrade that changes the numbers. The Skin Cancer Foundation describes UV window film as a thin polyester film with UV light inhibitors, in clear or tinted styles, that can block more than 99% of UVA and UVB when applied to glass. It suggests film on driver and passenger side windows and the sunroof.
Types of Window Tint Film
LLumar lists ceramic, metallized, dyed and clear constructions, typically applied to the inside of the glass, and says clear tint can be used on windshields. The 2025 paper notes that film on tempered glass has been reported to cut UV transmission by more than 99%.
Choosing the Right Tint: Look for UV Ratings
- Read the wording: LLumar says its tint blocks up to 99% of UV rays. Up to is a ceiling, not a guarantee for every film.
- Look for products sold as UV window film, solar window film or UV window tint. The Skin Cancer Foundation says many films are only for design or darkening.
- Ask for separate UVA and UVB numbers. The foundation’s Seal of Recommendation requires data showing 99% or more of solar UVA and UVB.
- Do not judge by darkness. Clear film exists, and the 2025 authors note that added tinting is not the only way a window can attenuate UVA.
Legal Tinting Regulations
Darkness rules vary by state, and LLumar says state laws regulate the level permitted. The 2025 paper notes that U.S. rules call for at least 70% visible light transmission through windshields and side windows. Confirm local limits with an installer before choosing a film. For installer pricing, see our ceramic tint cost guide, and for product picks, best window tint for car and tinted glass for car.
Sunroofs and Rear Glass
Sunroofs are the easiest spot to forget. The foundation groups side, back and sunroof windows together as tempered glass that does not block UVA effectively, and lists the sunroof among the places to film. In the 2025 data the back window averaged 95.36% UVA reduction, still below the windshield. For a deeper look, see do UV rays go through car windows and does car glass have UV protection.
How to Check Your Car’s UV Protection
You cannot tell by looking. The 2025 authors could not identify glass type or treatments on inspection, and the 2025 Frontiers paper notes that makers treat window specifications as proprietary. The researchers measured with calibrated SolarMeter UV meters, so a UV reading is the real test; ask a tint shop whether it offers one for your windows.
Myths and What the Sources Say
| Myth | What the sources say |
|---|---|
| You cannot get sun damage in a car | The Skin Cancer Foundation says UVA passes through window glass and exposure adds up over time. |
| If glass blocks UV, I am covered | Glass blocks most UVB, but side windows averaged 88.78% UVA reduction in 2025 and one read 65.22%. |
| Darker tint means more UV protection | The foundation says many films are only for design or darkening; clear UV film exists. |
| Every window on a car is the same | Windshield 99.25% against driver’s side 88.78% in the 2025 data. |
| Newer cars have solved this | Averages improved from 71% in 2014 to 88.78%, but model year did not predict driver’s side results. |
| Sunscreen is for the beach only | The foundation’s car travel tips name sunscreen, protective clothing and sunglasses for road trips. |
Parked car heat and dashboard fading are a separate problem from skin exposure; see best UV protection for a car interior and do car sun shades really work.
Protecting Yourself and Your Passengers
- Use film on the driver and passenger windows and sunroof if you drive often in strong sun (Skin Cancer Foundation).
- Wear sunscreen labeled broad spectrum, clothing that covers the arms, and UV-blocking sunglasses (Skin Cancer Foundation, CDC).
- For babies, the foundation says hats and clothing are the best protection, and the FDA says sunscreen is not recommended under six months.
- Move shade onto the glass: cling or mesh shades add cover on side windows, as covered in our car window shade guide.
Compare other UV approaches in UV protection for car windows. The 2025 study details are in the open paper, Axelson et al. (NIH PubMed Central).
Frequently Asked Questions
Do car windows block UV rays?
Mostly UVB and much of UVA. The 2025 study measured 88.78% to 99.25% mean UVA reduction depending on the window, while the Skin Cancer Foundation says UVA still passes through glass.
Does a car windshield block UVA?
Mostly. The 2025 study averaged 99.25% UVA reduction for windshields, with a lowest single reading of 91.67%.
Do side windows block UV?
Less than the windshield: 88.78% (driver’s) and 88.99% (passenger) mean UVA reduction in the 2025 study, with a low of 65.22%.
Does window tint block UV?
Some films do. The Skin Cancer Foundation says UV window film can block more than 99% of UVA and UVB, but many films only darken.
Which side of the car gets more UV?
The driver’s side, per the Skin Cancer Foundation, which cites a long-time truck driver case and more left-sided skin cancers in the U.S.
Do sunroofs block UV rays?
Not reliably. The Skin Cancer Foundation says sunroof glass is usually tempered and does not block UVA well.
Can you get sunburn through a car window?
UVA can also lead to sunburn and passes through glass, per the Skin Cancer Foundation.
Conclusion
Windshields do the most work; side windows, rear glass and sunroofs let more UVA through, and film is the proven way to close that gap. Pair it with sunscreen, clothing and shade rather than relying on glass alone.
What This Guide Does Not Cover
- State tint darkness limits; check your state rules or ask an installer.
- Medical advice; ask a dermatologist about your own skin.
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