Privacy experts are demanding transparency after YouTube announced it would test using AI to estimate user ages in the US ahead of a wider rollout of the age check system.

Throughout the first half of August, YouTube will begin interpreting “a variety of signals” to determine if certain users are under 18. No new user data will be collected, but those signals could include things like “the types of videos a user is searching for, the categories of videos they have watched, or the longevity of the account,” YouTube said.

Anyone determined to be too young will automatically be hit with protections, with YouTube disabling their personalized advertising, “turning on digital wellbeing tools,” and “limiting repetitive views of some kinds of content” determined to be harmful or too mature.

YouTube claims it has been estimating age in other markets “for some time, where it is working well.” But it’s clearly not a perfect system, as the company has set up an appeals process for any adults accidentally flagged as teens by AI.

That appeals process seems problematic, privacy experts told Ars,  as it requires users to submit a government ID, credit card, or selfie to verify their actual age. YouTube does not specify in its blog what will happen with this data. Asked for comment, YouTube would only confirm to Ars that the company “does not retain data from” a user’s “ID or Payment Card for the purposes of advertising.”

“I think we can assume that means it will be retained for other purposes,” David Greene, senior staff attorney and civil liberties director for the Electronic Frontier Foundation (EFF), told Ars. But the lack of transparency leaves users guessing about those other purposes, as risks of leaks or breaches seemingly risk exposing vulnerable users who rely on anonymity to use YouTube.

Greene told Ars that YouTube’s statement on data retention is even weaker and stands in “stark contrast” to “hollow statements” sometimes made by companies, such as “we’ll do our best to protect your data” or “we’ve been assured that the third-party vendor we use will not retain the data.”