Mostly no - away from windows, indoor sunscreen adds little: lighting emits negligible UV and glass blocks the burning UVB.
The exception dermatologists care about: hours of daily direct sun through glass, because UVA - the photoaging wavelength - passes through ordinary windows. A desk against a bright window for years is a real cumulative dose. Decision rule: sunny window seat most days = broad-spectrum SPF 30 in the morning; interior rooms = optional. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper .
What to do
Common questions
Do I need sunscreen indoors?
Mostly no - but the window seat is the exception that dermatologists actually care about. The calibrated consensus: if you spend your day away from windows, indoor sunscreen adds little - overhead lighting emits negligible UV, and standard glass blocks the burning UVB. The exception is chronic close exposure to daylight through glass: UVA - the deep-penetrating, photoaging, pigment-driving wavelength - passes through ordinary window glass, and dermatology commentary makes the case for daily sunscreen for people whose desk or favorite chair sits in direct sun for hours a day. That maps to real life: a desk against a bright south window, eight hours a day, years on end is a genuine cumulative UVA dose - the same mechanism behind drivers' one-sided damage. The decision rule: working near a sunny window most days = yes, a morning layer of broad-spectrum SPF 30 (it doubles as your daily anti-aging insurance); interior rooms and brief window passes = optional. Whatever you choose indoors, the outside rule stands - the walk, the drive, the lunch break still count, so daily facial sunscreen is the simple habit that covers both cases.