Now many eyes are on Slack and how it performs after going public. The company is planning a “direct listing,” where it will not issue new shares to sell, but simply let its shares start trading on a stock market. Its share price will be set solely by demand from public-market investors.

Slack also faces a crucial test as it transitions from a viral chat app to a more traditional operation selling workplace technology to global corporations. It will be no easy task as Mr. Butterfield deals with competition from Microsoft, which offers a product called Teams, and as Cisco and Facebook push similar tools. Slack is small compared with those giants; on Friday, it disclosed that it lost $32 million in the first quarter, while revenue rose 67 percent from a year ago to $135 million.

“There is one set of skills in making technology find the lips of all young developers around the world,” said Michael Facemire, an analyst at Forrester. “There’s another set of skills to sell that into the enterprise.”

Mr. Butterfield appears to be feeling the weight of responsibility. In April, at a conference Slack holds for customers and partners in San Francisco, he riffed in an onstage interview with the tennis megastar Serena Williams about how much rested on his shoulders.

“The success of the business, the happiness of the employees, its impact on customers — all that stuff,” he said. “It can be a lot to manage.”

Mr. Butterfield, who spent his early years at a commune in British Columbia, was named Dharma at birth. At age 12, he changed his name to Daniel. (Stewart is his middle name.) At the University of Victoria, where he studied philosophy, he discovered Usenet, email and Internet Relay Chat — the web protocol that forms the basis of Slack.