Slack Technologies Shares Extend Gain After First-Day Pop

Allen Shim, chief financial officer of Slack Technologies Inc., left, and Stewart Butterfield, chief executive officer of Slack Technologies on the floor of the New York Stock Exchange (NYSE) during the company's initial public offering.

Photographer: Michael Nagle/Bloomberg
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Slack Technologies Inc. shares rose as much as 4.2% on Friday in their second day of trading.

The maker of software for workers to chat and collaborate on projects traded as high as $40.25 in New York. In Thursday’s debut, the stock opened at $38.50, well above the reference price of $26.