For years, Facebook’s sneakiest data-collector has been the “Like” button. Any site that wants Facebook traffic needs one, which means they’re just about everywhere. And in order to work right, the button needs to log you in — which is to say, it needs to know who you are. How else would Facebook know who liked the post? Even if you don’t click, Facebook registers that you loaded the button, which means they get a map of every Like-enabled site you’ve been to, just the kind of data that advertisers will pay to target against.

Today at WWDC, Apple took a direct shot at that system and Facebook itself. Onstage, Apple’s VP of software Craig Federighi described Safari’s new anti-tracking features in unusually confrontational terms.

“Do you want to allow facebook.com to use cookies?”

“We’ve all seen these like buttons and share buttons,” Federighi told the crowd. “Well it turns out, these can be used to track you, whether you click on them or not. So this year, we’re shutting that down.”

When the new pop-up appeared, asking for permission to track him, the demo wasn’t shy about naming names: “Do you want to allow facebook.com to use cookies?” It was an unusually direct call out, on a level with the now-standard pokes at Android fragmentation. And coming after months of close scrutiny, Zuckerberg makes for an easy target. But there’s a real power shift behind the onstage jab, and it’s something that could quickly catch on with other browsers.

In technical terms, the change has to do with how Safari loads content, and how much information it gives to the site it’s loading. Browsers typically offer up your login token to any plug-in that asks for it, but the new Safari holds back, asking for specific permission before telling “share” buttons or comments sections who you are. That also applies to Facebook comments on third-party sites, the specific feature demoed by Federighi. Facebook was the company called out onstage, but it also has real consequences for Google, Facebook’s only real competitor in targeted ads.

There are other ways to track people on the web, but Safari takes aim at some of them, too, pulling back information on existing plug-ins, fonts, and other configurations. In Federighi’s terms, the result is to “make your Mac look like all the other Macs,” which makes it harder for advertisers to track you passively. It’s a major technique, and it will be a lot harder to pull off in the new Safari.

As always, Apple is playing to its advantage as one of the few major tech companies that doesn’t rely on targeted ads to make money — and taking a clear shot at how both Google and Facebook make their money. The data collected by Like buttons and other tracking pixels translates directly into ad dollars for Google and Facebook, which means the Safari shift will have a real impact on both companies’ bottom line. If Facebook doesn’t know you visited the Timberland store, it can’t serve you Timberland ads, and your every page view becomes that much less valuable. After months of free-floating privacy concerns (and undaunted user growth), this is one protest that has real sting to it.

It’s not the first time Apple has used Safari to take a shot at web tracking. Last year’s WWDC introduced Intelligent Tracking Prevention, which took particular aim at third-party tracking cookies while leaving login-based systems like Facebook and Google largely untouched. This year’s changes go further, and they also start putting real friction on the user, adding new dialogue boxes to click for anyone who actually wants to like a post. In theory, there’s a real risk of blowback to Safari. If it’s harder to use Facebook on Apple’s browser, users might stay on Chrome or switch over to Firefox. But after months of data panic, that threat isn’t nearly as scary as it used to be.

In some ways, the big picture is even scarier for Facebook. Safari isn’t a market-moving player in the browser space, and these moves didn’t merit more than a minute on stage. But this won’t be the last time a tech company sees a chance to score points by putting a dent in the digital advertisement juggernaut. The question will be how many dents it takes to make a difference.