SAN FRANCISCO -- Facebook will soon start tracking what users in the U.S. do not just on Facebook but also on other websites and apps to more effectively target them with ads.
The practice is common -- even for some ad networks Facebook partners with -- but the social network had previously based its ads mainly on what people did on Facebook, such as what pages they liked.
Users "want to see ads that are more relevant to their interests," Facebook said in an announcement about the changes Thursday.
For those weary of Facebook analyzing even more about their online behavior, the company offered this: "If you don't want us to use the websites and apps you use to show you more relevant ads, we won't. You can opt out."
The company noted that this kind of tracking was common at other companies. But Facebook claims it's going to do something other companies don't: allow users to see exactly why a targeted ad was displayed to them.
They can then add or remove interests that Facebook is basing its selection of ads on. "So if you're not interested in electronics, you can remove electronics from your ad interests," the company said.
The move is aimed at boosting advertising revenue, allowing Facebook to argue that its knowledge about users is richer, and that it has buy-in from the users themselves, with a say over what kind of products they want to be pitched.
Jeff Chester, executive director of the Center for Digital Democracy, expressed "serious concerns" about the changes.
"Providing further info on why a user is being targeted is insufficient," he said.
Facebook plans to roll out the changes for U.S. users in the next few weeks and is ramping up to make similar changes around the world in the coming months.