The privacy setting almost nobody turns on (and takes 90 seconds)

Every phone now ships with a setting that quietly limits how much advertisers can stitch your activity together across different apps. It is not hidden exactly. It is just buried one menu deeper than anyone goes by default, so almost nobody has touched it.

On iPhone, it lives under Privacy & Security → Tracking, and defaults to allowing apps to ask permission — the ask itself is often a formality most people tap through without reading. On Android, the equivalent lives under Privacy → Ads, as an opt-out of ad personalization entirely. Ninety seconds, both platforms, done.

What actually changes: apps can still show you ads. What stops is the cross-app profile-building — the reason a thing you searched in one app starts appearing as an ad in a completely unrelated one. That correlation is the product being sold about you, not the ads themselves.

I do not think this fixes privacy. I think it is the highest-leverage 90 seconds available to anyone who has not looked at their settings since setup day. Small lever, real effect, already sitting in a menu you own.