“Twitter shares certain non-public personal information with certain digital advertising platforms to help measure and optimize the effectiveness of our efforts to market Twitter on those platforms. This information can include IP address and mobile device advertising identifiers for devices that open or log in to Twitter’s mobile apps; but does not include your name, email, phone number, or Twitter username.”
The change has been applied worldwide to the latest versions of the app and online, but does not apply by default to countries within the EU, European Free Trade Association or the UK. Users in these nations will have to opt-in to the setting, which is off by default.
In the app’s settings, the option labelled “Share your data with Twitter’s business partners” used to stop the sharing of this ad information with Twitter. After the change, the setting still exists but does not include user control over this data. It now is only an opt-out setting for you to choose if Twitter can see additional user information.
A Twitter spokesperson told The Verge that 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.”
The change should not worry you too much given the data is anonymised. It is a sign that Twitter is trying to ramp up its effectiveness as a profit-making business though, given it is widely seen to be a stagnant platform by investors, who think it should be making a lot more money than it is.