Yes—unevenly. The windshield does most of the work. Side and rear windows leak a lot of UVA, which is the long-term damage band, not the sunburn you notice after a beach day.

Why the front glass is different

Windshields are laminated: two glass sheets around a plastic PVB layer. That interlayer is what blocks about 94–98% of UVA and nearly all UVB. Side and rear glass is usually tempered, with no plastic layer. They still stop almost all UVB, but often only 60–71% of UVA—so a third or more of UVA still reaches the window-side arm and face.

You are unlikely to sunburn through closed glass (UVB is handled). You can still accumulate UVA without turning pink. Rolling the window down removes even the partial filter. Same physics at home: does glass block UV?

Sunroofs are closer to side glass

Factory sunroof panes are typically tinted tempered glass—ballpark 50–70% UVA, not windshield-grade. An open roof or a convertible is outdoor UV. Aftermarket film on side windows can push blocking into the 85–99% range depending on the product; factory tint varies by car and is rarely published as a UV spec.

Short trips: probably fine. Hours a day in summer sun: sunscreen on the window-side skin, UV400 glasses, and a sleeve if you live in the car. Check the live UV index on High days the same way you would for a walk.