Apple is warning online advertisers and web developers it'll consider blocking them if they're ever caught covertly tracking user activities via the Safari browser.

Cupertino issued the warning in a new policy for WebKit—Safari's browser engine—which outlines the online web tracking Apple wants to prevent. Essentially, the company is forbidding any kind of tracking without the user's consent or knowledge.

"If a party attempts to circumvent our tracking prevention methods, we may add additional restrictions without prior notice," the policy says. "These restrictions may apply universally; to algorithmically classified targets; or to specific parties engaging in circumvention."

No exceptions will be given to specific parties either. "We treat circumvention of shipping anti-tracking measures with the same seriousness as exploitation of security vulnerabilities," the policy adds.

Two years ago, Apple took a harder line against web trackers by adding a privacy capability in Safari designed to prevent "cross-site" tracking, which is used across the ad industry to learn what sites your computer is visiting. Online marketing firms and tech companies such as Facebook can pull this off because their tracking scripts are embedded across thousands of websites through plugins or ads, which can identify and tag your machine with internet cookies.

Although the tracking can help companies personalize ads, it also means they can build a profile of your browsing habits without your consent. In response, Apple began restricting certain first-party cookies from tracking users beyond a 24-hour window. A year later, the company took aim at Facebook's tracking scripts by adding a Safari feature that can shut them down when encountered on a website.

"WebKit will do its best to prevent all covert tracking, and all cross-site tracking (even when it's not covert)," Apple's new policy adds. "If a particular tracking technique cannot be completely prevented without undue user harm, WebKit will limit the capability of using the technique. For example, limiting the time window for tracking."

The policy goes on to state the company will prioritize user privacy over preserving current industry practices that can help website owners measure user traffic, create personalized ads, and detect fraud or bots.

"However, we will try to limit unintended impact. We may alter tracking prevention methods to permit certain use cases, particularly when greater strictness would harm the user experience," the company said. "In other cases, we will design and implement new web technologies to re-enable these practices without reintroducing tracking capabilities."

Apple's move was inspired by Mozilla's anti-tracking policy, it said.

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