Slack

Slack Technologies makes Slack, a messaging and collaboration platform where teams work in channels and connect thousands of third party applications. The company was founded in 2009 in Vancouver as Tiny Speck by Stewart Butterfield, a co-founder of Flickr, with Eric Costello, Cal Henderson and Serguei Mourachov. Tiny Speck first built the online game Glitch, which launched in September 2011 and shut in December 2012; Slack grew out of the internal chat tool the team used while building it. The company later operated from San Francisco.

Tiny Speck raised $1.5 million of angel funding in 2009, a $5 million Series A from Accel and Andreessen Horowitz in 2010 and a $10.7 million Series B in 2011. After Glitch closed, Slack raised $42.75 million in April 2014 and $120 million in October 2014 at a $1.2 billion valuation, led by Kleiner Perkins and GV. In 2015 it raised $160 million at a $2.76 billion valuation, with Social Capital among the leading investors. In April 2016 it raised $200 million led by Thrive Capital, with GGV Capital, Comcast Ventures, Accel, Index Ventures and Social Capital participating. In September 2017 it raised $250 million, mostly from the SoftBank Vision Fund, bringing total funding to $841 million at a $5.1 billion valuation.

Slack went public through a direct listing on the New York Stock Exchange on June 20, 2019 under the ticker WORK, without raising new money. Shares opened above $41 against a $26 reference price. At the listing, the largest outside holders were entities affiliated with Accel (23.8%), Andreessen Horowitz (13.2%), Social Capital (10.1%) and SoftBank (7.3%). Its listing documents reported more than 10 million daily active users and more than 95,000 paid customers as of April 30, 2019. Revenue reached $903 million in 2020. On December 1, 2020 Salesforce agreed to buy Slack for $27.7 billion, and the deal closed on July 21, 2021. Slack now operates as part of Salesforce and reports more than 200,000 paid customers.

Slack is a well known pivot case: Accel and Andreessen Horowitz backed a game studio in 2010, and the product that returned their capital was the studio's internal chat tool. Accel's position of nearly a quarter of the company at listing shows how far an early fund can carry its ownership through later rounds. The path from founding to the 2021 sale took about twelve years, and the direct listing gave existing holders liquidity two years before the acquisition.