Roku, the online streaming box business, went public at a price of $14 per share. It nearly doubled its value in two days, closing at over $26 a share, with a market capitalization of over $2.5 billion. The company still faces competition from tech titans than are not dependent on revenues from their boxes.

Roku raised around $219 million by going public, having previously raised more than $200 million in venture funding. The company received revenues of $399 million in 2016, three quarters of which came from hardware sales, but reported a loss of $43 million.

Investors have bought into the promise that people are increasingly streaming programming to their television. Roku has managed to gain significant market share for its streaming boxes amid competition from bigger players like Apple, Alphabet and Amazon.

In mid-2017 Roku had over 15 million active accounts. Roku is bidding to increase revenues from the platform services side of its business, including advertising, but the path to profitability remains uncertain.

The problem is that Apple, Alphabet and Amazon all have other sources of revenue, whereas Roku is dependent upon sales of its streaming box hardware and associated services, and licensing its technology to television manufacturers.

In a statement, chief financial officer Steve Louden said Roku was number one in the market and has been competing effectively against Apple, Alphabet and Amazon for many years. “The platform business is growing at roughly 100 percent, year over year, and it’s extremely high margin,” he wrote. “It has gone from being about a third of total gross profit to over 80 percent of the gross profit in the first half of the year.

Roku products range from the Roku Express, which competes with the Google Chromecast and Amazon Fire Stick, to the Roku Ultra, which offers support for 4K resolution at 60 frames per second, competing with the Amazon Fire TV and Apple TV.

Apple recently released a 4K version of its Apple TV product, at price points of $179 and $199. That is significantly more than Roku or other competing products and it currently offers fewer channels, although the user interface is gorgeous.

Amazon is due to release a 4K Fire TV dongle, or perhaps that should be a dangle, designed to plug into the HDMI port on the back of a television. Priced at $69.99, it comes with a remote control that supports Amazon Alexa, with the capability to control other connected home devices.