GOOGLE'S NEW AD BLOCKER CHANGED THE WEB BEFORE IT EVEN SWITCHED ON

You might see fewer ads on the web from now on. But you probably won't.

On Thursday, Google Chrome, the most popular browser by a wide margin, began rolling out a feature that will block adson sites that engage in particularly annoying behavior, such as automatically playing sound, or displaying ads that can't be dismissed until a certain amount of time has passed. Google is essentially blacklisting sites that violate specific guidelines, and then trying to filter all ads that appear on those sites, not just the particularly annoying ones.

Despite the advance hype, the number of sites Chrome will actually block ads on turns out to be quite small. Of the 100,000 most popular sites in North America and Europe, fewer than one percent violate the guidelines Google uses to decide whether to filter ads on a site, a Google spokesperson tells WIRED.

But even if Chrome never blocks ads on a page you visit, Google's move has already affected the web. The company notified sites in advance that they would be subject to the filtering, and 42 percent made preemptive changes, the spokesperson says, including Forbes, Los Angeles Times, Chicago Tribune, and In Touch Weekly.

It may seem strange that Google, which still makes most of its revenue from advertising, blocks ads at all, especially since the company says it will even block those served by its own ad networks. But Google hopes ridding the web of its very worst ads might discourage Chrome users from installing more aggressive ad-blocking software that saps revenue universally.

A survey published by the industry group Interactive Advertising Bureau in 2016 found that about 26 percent of web users had installed ad-blockers on their computers, and about 15 percent had ad-blockers on their smartphones. Respondents gave a variety of reasons for blocking ads, including privacy concerns, page load times, and visual clutter.