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.

The ads will be shown to users only within WhatsApp’s “Updates” tab to separate them from people’s personal conversations.