There's a major tech battle coming over privacy and tracking. Based on a recent announcement from Apple, it appears set to begin in early 2021, when Apple will begin enforcing a change that will restrict third-party cookies from tracking user activity without express consent.

Apple isn’t necessarily going to war with the digital and mobile ad industries, but the privacy feature is among the iPhone maker’s most aggressive developer policy changes it has introduced in recent memory. First revealed at this year’s WWDC in June, the new feature will show users a prompt when an app has requested their so-called Identification for Advertisers, or IDFA, code. Many users are expected to decline, and Facebook has said the feature may “severely impact” its ad network, according to a report from Bloomberg last week on the social network’s decision to stop collecting IDFA codes altogether.

This move will have major implications for Facebook, as well as businesses that advertise on the Facebook ad network. Social media advertising is a major channel of customer acquisition for ecommerce brands. By restricting third-party tracking, it will be incredibly difficult to track the success of ad campaigns because no data will be shared to report upon the result of the click. That includes whether a user made a purchase at all.

Apple's announcement mentioned that the 2021 rollout is designed to give advertisers & developers time to prepare for the changes. Of course, this only affects Apple devices leaving all non-apple users open to third-party tracking, at least initially. It seems natural that each of the major platforms may become more protective of user data and follow suit with similar moves.