SAN FRANCISCO — Slack, a workplace messaging company, said Monday that it had confidentially filed paperwork for an initial public offering, joining the growing number of technology start-ups heading to the stock market.
Slack, which is based in San Francisco, gave no details about the offering’s timing and said it was awaiting a standard review of its paperwork by the Securities and Exchange Commission. The move was expected given that Slack’s chief executive, Stewart Butterfield, had long indicated that he planned to take the company public. Slack recently hired Goldman Sachs to lead the offering.
Slack’s confidential filing comes amid a rush by privately held companies to go public this year. Many of these start-ups, which have been highly valued by private investors, are part of a generation of technology companies known as unicorns. Public share sales by the companies are expected to create a bonanza of riches in Silicon Valley for entrepreneurs and venture capital investors.
In December, the ride-hailing companies Uber and Lyft filed confidential paperwork for their own public offerings. Their efforts stalled temporarily last month when a government shutdown hampered the S.E.C.’s ability to review the companies’ registration documents. Other tech companies expected to go public this year include the online scrapbooking firm Pinterest.
Slack declined to comment beyond its statement about the confidential filing.
There is likely to be a strong demand for Slack stock. The company was valued at $7.1 billion by private investors last year, but in recent weeks investment firms have offered to buy its shares at a price that values Slack at $13 billion, according to a person with knowledge of the details who was not authorized to speak publicly.
Slack also plans an unusual form of public offering called a direct listing, the person added. Unlike most I.P.O.s, in which firms sell stock to public market investors in advance, direct listings let a company begin trading its shares on an exchange without raising new funds. Spotify, a provider of streaming music, went public in 2018 in a direct listing, paving the way for other high profile start-ups to follow.
With a direct listing, shareholders can also sell their stock immediately after the public offering, instead of waiting for what is known as a lock-up period to expire.
Slack has little need for cash. It raised $427 million in new financing in August, a year after raising $250 million. The company has collected a total of more than $1 billion from investors that include the SoftBank Vision Fund, General Atlantic, Dragoneer Investment Group and T. Rowe Price Associates.
Mr. Butterfield began Slack out of a gaming start-up called Tiny Speck. While the company’s game products failed to take off, its internal communication tool showed promise. In 2014, the company began selling that communication tool, called Slack.
Start-ups quickly adopted Slack and larger companies followed suit. The company offers free and paid versions of Slack and counts more than 85,000 paying customers, including 65 Fortune 100 companies. Last month, Slack said 10 million people now use its product every day. The company generated more than $350 million in revenue last year, said the person with knowledge of the details.
Some companies that have filed to go public have never reached that finish line. Over the last year, a number of high-profile business software companies that took steps to go public were snapped up by a tech giant at the last minute. In November, for example, Qualtrics, an analytics start-up, sold to SAP for $8 billion just days before it was set to ring the opening bell at Nasdaq.
Google, Microsoft and Amazon have previously expressed interest in acquiring Slack, but the company has demurred. Now some of them have increasingly begun to compete with the start-up. Microsoft, for one, created its own workplace messaging company called Microsoft Teams. When Teams launched in 2016, Slack took out a newspaper ad directed at its new competitor.
“We’re genuinely excited to have some competition,” it read.
In January, Microsoft announced that 420,000 organizations use its Teams product, including 89 of the Fortune 100.