Opting out of WhatsApp’s controversial new terms doesn’t actually stop it sharing information with Facebook.

The company provoked outrage this week when it announced that it was changing its terms to allow it to share user data with parent company Facebook. The announcement was doubly controversial since both WhatsApp and Facebook committed to keeping user information separate when the messaging app was bought.

Some of the anger was calmed by the fact that WhatsApp gave its users the ability to opt out of the deal, so long as they did so within 30 days of the change. Doing so is relatively simple, and can be done in one of two ways. But it appears that asking to be opted out doesn’t actually stop the sharing deal in its entirety. Some key information will still be sent to Facebook, and there is nothing users can do to stop it.

Opting out does stop WhatsApp sending information to Facebook for “ads and products experiences”. That means that Facebook won’t be able to use information about who people are talking to for its advertising, meaning that WhatsApp data won’t make a difference to what shows on Facebook and vice versa.

But it doesn’t opt people out of the various other data sharing agreements that WhatsApp has made with Facebook. WhatsApp only says that sharing is for “other purposes” – thought to refer to things like fighting spam and improving security on both platforms, but potentially other uses too.