The social network debuted new features on Tuesday intended to alert people when someone else has uploaded a photo of them, even if they weren’t “tagged” in the photos with their real names. Users can then approve the image for publishing, choose for it to be untagged without their names, or contact the person who uploaded the photo.

The new feature is built using the same underling facial recognition technology that Facebook uses to recommended who to tag in photos before they are uploaded. This technology, which Facebook has been using since 2010, can compare human faces in new photos with stored data on Facebook to determine who the person is.

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Facebook’s facial recognition technology also powers a new feature that automatically notifies people if someone uploads a profile photo of them to create bogus accounts. Facebook’s applied machine learning project manager Nipun Mather acknowledged that impersonation is a minor but important problem on Facebook, but he did not reveal more details about the number of incidents.

Facebook is also debuting a way for people to opt-out of using the company’s facial-recognition features by toggling an “on-and-off switch,” said Facebook’s deputy chief privacy officer Rob Sherman.

“We want to make sure it’s possible to turn them off if for whatever reason they don’t want to participate,” Sherman said about what he described as an “easy” way to opt-out of features using facial-recognition technology.

Whenever a user turns off the facial recognition technology, the data Facebook collects to determine one’s face—which Facebook calls a “template”—will be destroyed, Sherman said. People who currently have chosen against taking part of Facebook’s existing photo tagging service will have their current settings applied to the expanded use of facial recognition technology.

Facial recognition is a controversial subject for privacy advocates like the American Civil Liberties Union, which worry about the growing use of the technology for government and corporate surveillance. They are also worried about the use of facial recognition without public consent.

Facebook (FB) is the target of a class-action lawsuit in Illinois over allegations that its facial-recognition technology violates the state’s privacy and data collection laws. Google (GOOG) and online photo service Shutterfly also face similar lawsuits in the state.

A Facebook spokesperson said these lawsuits had nothing to do with Facebook’s new features. Sherman said the company developed the features based on feedback from its users and its regular discussions with privacy experts, in an effort to create a system that is transparent to users.

The new features will not debut in Canada and Europe where lawmakers in those regions are especially wary of facial-recognition technology.

“The goal here is part of a broader effort to be communicative to people about privacy,” Sherman said.