If you're a Google user—and who isn't these days—you'll soon get a notification suggesting you check in on your security settings. You definitely want to do this, because there's a major change in there. Even more major? That Google has made it opt-in.

The prompt includes an option to let Google use all of the information associated with your account—search, Chrome, YouTube, the works—to inform the ads you see across the web. Google already does this within its own services, but until now it has used cookies for anything beyond that.

This new setting would change that.

Opting in gives you more granular control over how ads work across devices signed into your Google account. If a search for boat shoes (you know, the grey ones with white laces) haunts you across the web, you’ll be able to kill it everywhere, all at once, rather than going device by device.

Google’s also introducing My Activity, a page that bundles search history, videos you've watched, and pages you’ve visited that serve Google ads. Opt in to the new setting, and you'll be able to comb through your online life in far finer detail. That fine-tuning won't all come today, but instead will roll out gradually over time. Google says it will continue to refrain from sharing your data, and you can tweak the type of information it collects from the My Account page.

The move to use your Google information across the web echoes a similar endeavor from Facebook, with a key difference: Google lets you opt-in to the program, rather than requiring you to opt-out. That’s one reason Google is broadcasting it so loudly—you can’t enlist in something you don't know about. Google users will see the notification until they act on it.

“The fact that it’s an option, and that the user has to think through some of the account, and ad, and other implications of it, is really the best thing about it," says Brenda Leong, of the Future of Privacy Forum, a think tank funded largely by corporations (including Google) that focuses on data privacy best-practices.

If you’re a privacy hawk, you’ll probably want to keep your settings as-is. Google appears to be gaining more than its users here, and your ad blocker makes most of this moot. But if the idea of a more extensive search history and greater control over the ads you see is appealing, you’ve got the option to fiddle to your heart’s highly relevant content. More importantly, no one's making that choice for you.