The stock opened at $38.50, nearly 48% above a reference price of $26 set by the New York Stock Exchange on Wednesday.

Slack is the second high-profile technology company after Spotify Technology SA to opt for a direct listing over a traditional IPO.

The direct listing could further pave the way for companies looking to go public without the aid of Wall Street underwriters, who charge millions of dollars in fees.

(Reporting by Bharath Manjesh in Bengaluru)