By default, Facebook tracks what you do even when you’re not on Facebook, like the products you shop for, the political candidates you donate to, and the porn you watch, using tools like Facebook Pixel, a small piece of code deposited on millions of websites across the internet. The social network uses that information to target you with personalized ads—a business model that is now worth billions of dollars.

But that model has also come under increased scrutiny as privacy advocates, lawmakers, and pundits continue to question why anyone should trust Facebook with their data. In the aftermath of the Cambridge Analytica scandal last year, Facebook promised that users would soon have more control over their information using a “Clear History” tool, which would delete people’s off-platform browsing records. More than a year later, the company finally announced Monday it’s rolling out the feature, now called “Off-Facebook Activity.” People in Ireland, South Korea, and Spain will have access to the long-anticipated tool first, and it will be rolled out in the coming months to all Facebook users.

Louise Matsakis covers Amazon, internet law, and online culture for WIRED.

Off-Facebook Activity will give you a summary of the third-party websites and apps that share your visit history with Facebook, and will allow you to clear them. You can also choose not to allow Facebook to use your browsing history for personalized advertising in the future, including on Messenger and Instagram. Erin Egan, Facebook’s chief privacy officer, and David Baser, the director of product management, noted in a blog post that the new tool “could have some impact” on Facebook’s business, but that “giving people control over their data is more important.”

But not complete control. Even if you turn off Facebook’s ability to use your browsing history for ads, Facebook will still collect that information, and it will still be connected to your account for up to two days. Buried in a Help Center post behind a drop-down menu, Facebook clarifies: “Your future off-Facebook activity will be disconnected within 48 hours from when it's received. During this time it may be used for measurement purposes and to make improvements to our ads systems.”

In an email, Jay Nancarrow, Facebook’s director of policy communications, said that Facebook will notify users of this 48-hour period when they access the“Manage Future Activity” portion of the tool in their settings. He also noted that the caveat was included in an engineering blog post Facebook published Monday explaining how Off-Facebook Activity was built.

Even after 48 hours, the Off-Facebook Activity controls won’t actually delete your browsing data from Facebook’s servers. It merely decouples the information from your personal profile. Your data will still show up in aggregated contexts. “This way, we can do things like give advertisers reports on the effectiveness of their ad campaigns or give businesses aggregated site and analytics reports, such as how many women between the ages of 18 and 24 use their apps,” Nancarrow said. And Facebook needs the 48-hour window in order to compile this kind of information. In a blog post aimed at clients published in May, Facebook reassured advertisers it would “still be able to provide accurate measurement,” in order to help businesses grasp “the impact of their Facebook investment.”

“Facebook is essentially saying, ‘We’re just going to remove the link between your unique Facebook account and this big stream of data, but we’re going to keep that big stream of data,’” said Aaron Rieke, the managing director of Upturn, a nonprofit research group that has studied Facebook’s advertising practices.

Facebook says it’s choosing to decouple your data instead of deleting it not just for business reasons but also technical ones. In its technical blog post laying out how the new tool was built, Facebook’s engineers explained that the company stores user information across various scattered databases, rather than in one centralized location. Because deleting data across them all might not work reliably, Facebook chose instead to “disconnect it directly from a person’s account.” Facebook says it believes the tool is unprecedented, meaning there was no roadmap it could follow to build the feature.