China's iPhone users have found a new craze โ€“ a new app called Zao which lets people convincingly and hilariously transpose their faces onto actors like Leonardo DiCaprio, Kit Harrington from Game of Thrones, and many others.

Zao topped the Chinese iOS download chart over the weekend after first launching on the App Store on Friday. As of Monday, Zao remains top of China's App Store, according to App Annie.

It isn't currently available to anyone without a Chinese phone number, and isn't listed on the UK or US App Store or Play Store.

Created by Chinese developer MoMo, the app allows users to deepfake their faces onto a huge range of actors, singers, and even video game characters. Users can upload even just a single image of their face and the app will automatically map it onto selected video clips for them. The results are surprisingly convincing and unexpected.

So-called "deepfake" technology has caught the public's imagination, using AI software to analyse someone's face and then map it onto video of someone else. Recently it has become more sophisticated and, as the Zao app shows, more accessible.

Check out some Zao-generated deepfakes below:

This tweet from game developer Allan Xia shows his face grafted onto various shots of Leonardo DiCaprio.

Xia also had a dialogue with himself as both Jon Snow and Samwell Tarly from Game of Thrones.

The app has GIF-generating functionality, as illustrated by this gif of Xia as Wolverine.

It also appears to work with video game characters, here's Xia inserting his face into Devil May Cry.

Finally Xia replaced a K-Pop singer's face with his own.

Twitter-user Nikk Mitchell also deepfaked his way onto DiCaprio's filmography.

Mitchell expressed his amazement at the app, mapping himself onto two Chinese actors.

Chinese technology commentator Matthew Brennan inserted himself into Big Bang Theory.

And Twitter user Andrew Rae transposed himself into Braveheart.

Zao isn't currently available to non-Chinese users, but it's raising some concerns around privacy and the ethics of deepfakes

Behind Zao is Momo, a large social-media company which owns Chinese dating app Tantan.

Bloomberg and The Guardian reported that after going viral, privacy concerns started to crop up from users who had seen a line in the app's terms and conditions which stipulated the app had "free, irrevocable, permanent, transferable, and relicense-able" to user-generated content.

The backlash promoted WeChat, China's popular chat service, to block Zao on its platform.

Bloomberg reports that Zao quickly updated its terms, saying "headshots" and "mini-videos" won't be used for anything other to improve the app, or anything else pre-approved by the user.

The sudden backlash is reminiscent ofย the mistrust that surrounded FaceApp, a Russian app which used AI to apply various filters to users' faces to make them appear old or switch gender.

Zao also said in a statement, according to Bloomberg: "We understand the concern about privacy. We've received the feedback, and will fix the issues that we didn't take into consideration, which will need a bit of time."

Should Zao decide to make its app available more widely, it's likely Western users will still feel concern. China has used facial recognition technology to massively expand its surveillance network, and users will likely baulk at handing over personal data to an overseas developer.

Chinese selfie app Meitu likewise went viral in the West in 2017 for its beautification of photos, but was criticised for demanding access to excessive data like phone numbers and GPS co-ordinates.

This article was originally published by Business Insider.

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