KEY POINTS
  • Slack investors are getting up to $28 a share to sell some of their holdings ahead of a public offering.
  • That price values the company at about $16.7 billion.
  • The shares were priced at $11.91 apiece in August at a valuation of just over $7 billion.
Stewart Butterfield, co-founder and chief executive officer of Slack Technologies Inc. at South By Southwest (SXSW) Interactive Festival on Tuesday, March 15, 2016.

As Slack gears up to hit the markets through an unconventional direct listing, stock activity is increasing on the private markets at a price that values the company at nearly $17 billion, according to Forge Global, a firm that matches private companies and their employees with investors.

In Slack's last financing round in August, the company sold shares at $11.91 apiece for a valuation of $7.1 billion. Some early investors and employees have been selling stock at around $28, Kelly Rodriques, CEO of Forge, told CNBC. At that price, they're valuing Slack at close to $17 billion.