WhatsApp has updated its terms and privacy policy, as it gears up to send its first ads to users.

The updated document – changed for the first time in four years, before the messaging app was acquired by Facebook – features a lot of small changes, referencing its ownership and more recent features like end-to-end encryption and its desktop app. But the biggest change is that WhatsApp will open up its user data to Facebook, “as part of our plans to test ways for people to communicate with businesses in the months ahead”.

Users phone numbers will be connected with Facebooks systems to link together accounts on the two services, in order to show WhatsApp users targeted ads based on Facebooks data on their demographic and interests.

“We want to explore ways for you to communicate with businesses that matter to you too, while still giving you an experience without third-party banner ads and spam,” reads WhatsApps announcement. “Whether its hearing from your bank about a potentially fraudulent transaction, or getting notified by an airline about a delayed flight, many of us get this information elsewhere, including in text messages and phone calls.”

These messages from businesses will start to roll out in the next several months.

Possibly in anticipation of user backlash to the announcement, WhatsApp has stressed its focus on user privacy, repeatedly referencing the introduction of end-to-end encryption earlier this year. The content of users messages still wont be available to Facebook – or indeed, to WhatsApp itself – and it pledges never to sell or give users phone numbers to advertisers.

“Our belief in the value of private communications is unshakeable, and we remain committed to giving you the fastest, simplest, and most reliable experience on WhatsApp,” the announcement reads.