The launch upends its founders’ original mission of creating an app with ‘No Ads! No Games! No Gimmicks!’ This week, WhatsApp did something its founders said it would never do: it’s putting advertisements inside the app. It ends WhatsApp’s decade-plus run of offering an ad-free messaging and calling experience.

WhatsApp says that users will start seeing ads in parts of the app, as owner Meta Platforms moves to cultivate a new revenue stream by tapping the billions of people that use the messaging service.

I talked with a professor of advertising to make sense of what this means for all of us who use those social media platforms.