Google will introduce an ad blocker to Chrome early next year and is telling publishers to get ready.

The warning is meant to let websites assess their ads and strip any particularly disruptive ones from their pages. That’s because Chrome’s ad blocker won’t block all ads from the web. Instead, it’ll only block ads on pages that are determined to have too many annoying or intrusive advertisements, like videos that autoplay with sound or interstitials that take up the entire screen.

Sridhar Ramaswamy, the executive in charge of Google’s ads, writes in a blog post that even ads “owned or served by Google” will be blocked on pages that don’t meet Chrome’s guidelines.

Instead of an ad “blocker,” Google is referring to the feature as an ad “filter,” according toThe Wall Street Journal, since it will still allow ads to be displayed on pages that meet the right requirements. The blocker will work on both desktop and mobile.

Google is providing a tool that publishers can run to find out if their sites’ ads are in violation and will be blocked in Chrome. Unacceptable ads are being determined by a group called the Coalition for Better Ads, which includes Google, Facebook, News Corp, and The Washington Post as members.

The feature is certain to be controversial. On one hand, there are huge benefits for both consumers and publishers. But on the other, it gives Google immense power over what the web looks like, partly in the name of protecting its own revenue.

First, the benefits: bad ads slow down the web, make the web hard and annoying to browse, and have ultimately driven consumers to install ad blockers that remove all advertisements no matter what. A world where that continues and most users block all ads looks almost apocalyptic for publishers, since nearly all of your favorite websites rely on ads to stay afloat. (The Verge, as you have likely noticed, included.)

By implementing a limited blocking tool, Google can limit the spread of wholesale ad blocking, which ultimately benefits everyone. Users get a better web experience. And publishers get to continue using the ad model that’s served the web well for decades — though they may lose some valuable ad units in the process.

There’s also a good argument to be made that stripping out irritating ads is no different than blocking pop ups, which web browsers have done for years, as a way to improve the experience for consumers.

But there are drawbacks to building an ad blocker into Chrome: most notably, the amount of power it gives Google. Ultimately, it means Google gets to decide what qualifies as an acceptable ad (though it’s basing this on standards set collectively by the Coalition for Better Ads). That’s a good thing if you trust Google to remain benign and act in everyone’s interests. But keep in mind that Google is, at its core, an ad company. Nearly 89 percent of its revenue comes from displaying ads.

The Chrome ad blocker doesn’t just help publishers, it also helps Google maintain its dominance. And it advantages Google’s own ad units, which, it’s safe to say, will not be in violation of the bad ad rules.

This leaves publishers with fewer options to monetize their sites. And given that Chrome represents more than half of all web browsing on desktop and mobile, publishers will be hard pressed not to comply.

Google will also include an option for visitors to pay websites that they’re blocking ads on, through a program it’s calling Funding Choices. Publishers will have to enable support for this feature individually. But Google already tested a similar feature for more than two years, and it never really caught on. So it’s hard to imagine publishers seeing what’s essentially a voluntary tipping model as a viable alternative to ads.

Ramaswamy says that the goal of Chrome’s ad blocker is to make online ads better. “We believe these changes will ensure all content creators, big and small, can continue to have a sustainable way to fund their work with online advertising,” he writes.

And what Ramaswamy says is probably true: Chrome’s ad blocker likely will clean up the web and result in a better browsing experience. It just does that by giving a single advertising juggernaut a whole lot of say over what’s good and bad.