Social media sensation Snapchat plans to float on the US stockmarket in an initial public offering (IPO) that could value it at around US$25 billion (£20bn). That would make it the largest IPO since Chinese internet giant Alibaba floated in 2014. Snapchat has reported above 100 million daily users, more than Twitter. It is popular among young people, who use it on their mobile phones to send ‘selfies’ that expire after seconds. The flotation could be as early as March 2017.