Snapchat's crazy face-swapping feature now lets you trade faces with the photos on your phone

Biz Carson/Business Insider

Snapchat's face-swapping feature can do some pretty nifty tricks, like replacing your cat's face with yours, if a friend is sitting next to you.

With an update on Thursday, the social sharing app now lets you swap faces with people from photos on your phone too. 

It works like this: On Snapchat's camera screen, tap and hold like your normally do to pull up the filters. Next to the face-swapping option, there's a new one to swap faces with photos on your phone's camera roll. When you select it, you'll see that Snapchat has already singled out faces from the most recent photos in your phone. 

To Snapchat's credit, they've done a great job seperating out the faces of people from those of animals or other things. Only one photo had my dog's face, despite having many more photos of my dog on my phone than people. 

It's also rare for the app to use photos stored on your phone at all, although you can send them via chat. 

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