Yes, you need sunscreen by the window.

Yes, if you sit near a window for more than a few minutes a day.

UVB rays—the ones that cause sunburn—get blocked by glass. UVA rays, which cause aging and skin cancer, go straight through. So you won’t burn, but your skin is still getting hit. That window is not a force field.

If you sit within arm’s reach of a window for hours (WFH desk, coffee shop couch, your favorite reading chair), treat it like being outside but without the burn risk. A lightweight moisturizer with SPF 30 is enough.

The car driving home is the same story. Those drivers who age on one side more than the other? That’s why.

Your skin does not know you’re inside.