WhatsApp said Monday 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.

They will appear in only one part of the Meta-owned messaging service, it said. The move is potentially lucrative, while raising questions about user privacy.

WhatsApp is rolling out new ad features including a subscription model that will allow channels to offer exclusive content for a monthly fee.