“We are committed to ensuring users can choose whether or not they allow an app to track them,” the company said in a developer update it posted on Thursday. “To give developers time to make necessary changes, apps will be required to obtain permission to track users starting early next year.”

While the policy is likely to be a major benefit to users, it has been controversial among some developers and advertisers. In particular, Facebook has warned it could have dire effects on its ad network. In testing, the company said it saw a 50 percent decline in Audience Network publisher revenue when ad personalization wasn’t available as an option. The company went on to say the anti-tracking feature could make it so that it might not make sense for Facebook to offer the tool in iOS 14.

Apple also provided an update on another privacy-related feature. By the end of the year, developers will need to include a privacy information section on their App Store listings that detail how their software collects and stores user data. By the end of October, Apple will start accepting this information from developers.

Cross-site tracking is the practice of monitoring a person’s browsing behavior. Often, it involves sharing data with third parties such as advertisers. If you’ve ever looked at a product on Amazon, and then seen ads for it follow you from website to website, you’ve been a victim of cross-site tracking.

As CNET notes, Apple isn’t the first tech company to announce a crackdown on cross-site tracking. In fact, in the document itself, Apple notes its new policy was inspired by Mozilla’s anti-tracking policy. However, the scale of the company and its cachet with both consumers and within the industry may turn the tide against the practice.

That said, as significant as Apple’s new stance against cross-site tracking is, it’s not even the most important privacy stance Apple has taken this year. At WWDC 2019 in June, the company announced “Sign in with Apple,” a new, privacy-focused login service designed to compete against similar offerings from Google and Facebook. One of the notable features of the service is that it will generate random emails to protect an individual’s primary email. Experts, however, aren’t in agreement whether the feature is a clear win for consumers.