Uber confidentially filed paperwork to go public on Thursday, sources told several news outlets late Friday. The Wall Street Journal was the first to report the news that officially begins the countdown for one of the most hotly anticipated and biggest stock market debuts in history. Uber filed the paperwork on Thursday, the same day as its smaller rival Lyft, setting the stage for a race to see who will be the first to get to the public markets in the first half of next year. “It sounds like Uber is trying to steal Lyft’s thunder,” said Matt Kennedy, senior IPO market strategist at Renaissance Capital, an institutional IPO research firm. “The first one to go to market will get more buzz and will set the valuation.”

Uber has been told the company could be worth as much as $120 billion, which could potentially turn the offering into the biggest since 2014, when Alibaba began trading on the New York Stock Exchange. Lyft could potentially seek a valuation as high as $30 billion. If Uber does go with the high end of the valuation it would represent a huge jump from August, when the company had been valued at $76 billion, notes the New York Times.

The listing of Uber is expected to be the largest market debut in a year in which several well-known Silicon Valley companies are expected to go public, including Airbnb and Slack. The public offering won’t just be a test of investor appetite for a company that has been plagued by controversy, both due to its business model and workplace practices. It will also test just how willing investors are willing to value popularity over profits. In the third quarter, Uber lost $1.07 billion on revenue of $2.95 billion.