Twitter has removed a privacy feature that allowed all users to stop sharing some private information with advertisers. The setting prevented Twitter from sharing information like the ads you saw or interacted with and the tracking identifier for your phone. For most users, that information will now be shared by default and can’t be turned off.

The shared data is used to show the efficacy of advertising on Twitter, the company says. It helps Twitter prove that people are actually watching, interacting with, and otherwise seeing the ads that advertisers are paying for, which helps the company “continue operating as a free service.”

Twitter wants more data to prove that its ads work

An option in Twitter’s privacy settings called “Share your data with Twitter’s business partners” used to let you disable sharing of this information. That setting still exists, but Twitter now says it has removed your control over “mobile app advertising measurements.” Disabling the setting can still prevent sharing of other information, such as your interests. Other Twitter privacy settings, like disabling web tracking, are still available. Twitter will not share your name, email address, phone number, or username.

There is one major set of exceptions: this mobile ad data will still be kept private for Twitter users in the European Union, the European Free Trade Association, and the United Kingdom. They’ll have to opt in to sharing the information should they wish to let Twitter share more information about them.

Twitter alerted users to the change with a pop-up when they opened the app starting around 11AM ET today. A Twitter spokesperson said the update is “part of our ongoing work around transparency and control. We want to ensure that people understand the settings we provide, what they do, and how to use them.” Even users who had not disabled sharing data received the alert.

The availability of ad data has had a big impact on Twitter’s earnings in the past. Last year, Twitter blamed an earnings miss on a bug that prevented it from properly using and sharing this kind of ad data. At the same time, Twitter mentioned that a bug had also caused the company to ignore some user settings to prevent certain data from being shared. While Twitter isn’t removing those settings altogether, today’s change seems to simplify things by giving Twitter more control in the first place.