Apple breaks its silence on the privacy crackdown that’s roiled the online ad industry

John Ternus' Apple is waging war on advertising identifiers.

Benjamin Fanjoy/Getty Images Apple roiled the ad industry with an unexpected new crackdown on web trackers.

The tech giant has now issued a rationale for why it's stamping out "identity resolution." The ad industry has concerns Apple's latest privacy move may hamper targeting and measurement.

Apple's latest privacy crackdown left the online ad industry scrambling for answers.

Now, the tech giant has finally offered some.

Late on Monday, Apple published a blog post laying out its rationale for new restrictions that block technology used to identify and track consumers across websites.

The changes are implemented through WebKit, the browser engine that powers Safari and other browsers on iPhones and iPads.

Apple said the change was designed to target " identity resolution ," a method adtech companies use to connect separate data points about users — such as email addresses, phone numbers, IP addresses, browsing history, or information about the device they're using — to identify and track them across devices.

The method grew in popularity as many web browsers, including Apple's Safari, began phasing out third-party tracking cookies , the small files dropped on a user's device that were traditionally used for web tracking.

The ad industry deploys tracking to precisely target specific audiences and measure whether their campaigns are working.

In its blog post , Apple said that while users might readily offer their email address to log in to a website or sign up for a newsletter, most wouldn't expect it to also be shared with other companies for invisible tracking purposes.

"It's not enough to block cross-site cookies to prevent cross-site tracking today because the tracking industry has not stopped trying to track users on the web," Apple said.

"They have ushered into what they call the post cookie era and in our latest releases we have put strong protection in place." The blog post explains that Apple is implementing "domain-level" blocking, a broad intervention designed to ensure that identity providers can't circumvent the restriction by changing how they send data.

Apple took the adtech industry by surprise earlier this month when it came to light that it had begun blocking the domains operated by several companies that offer alternative identifiers, without warning.