Slack's stock price opened at $38.50 a share Thursday, making the company's CEO Stewart Butterfield a billionaire.

The work-messaging company—trading under the aptly-named ticker symbol WORK—opened at $38.50, propelling it to a valuation of $23.2 billion. The opening price is a 48% jump on the $26 per share reference price set Wednesday afternoon. The reference price typically serves as guidance for where to start bidding, based on how company shares have fared in the private market. The stock soared to more than $41 at midday on Thursday, valuing the company at more than $25 billion.

Since no additional shares are being issued, Butterfield’s estimated 7% stake in the company gives him a net worth of $1.6 billion.

Slack is the latest tech company that has gone public this year. Uber, Lyft, and Pinterest stumbled out of the gate, but enterprise video company Zoom has fared far better than expectations.

In its entrance on the New York Stock Exchange, Slack became only the second large company, after music streaming giant Spotify, to carry out a direct listing instead of an IPO. A direct listing means that Slack isn’t issuing any new shares. Instead, current shareholders may trade their shares publicly. However, with no new shares, Slack isn’t raising any funds. In addition, existing shareholders won't have to wait 180 days before they can sell their stocks.

Slack had about $800 million in total cash, cash-like assets and marketable securities at the end of April and has raised about $1.2 billion so far from private investors, according to the company’s regulatory filing.

Slack is an internet-based platform that allows teams and businesses to communicate with each other. It organizes discussions by topic and group, is similar to instant messaging chatrooms, and allows cooperation on documents and files.

Launched in 2013, Slack has replaced e-mail discussions at many companies.

The San Francisco-based company said it ended the first quarter with 95,000 paid customers. Slack had also more than 500,000 organizations on its free subscription plan, as of Jan. 31.

Slack is competing with Microsoft Teams, a free chat add-on for Microsoft’s Office365 users. Other similar platforms include Google Hangouts, Workplace by Facebook and Cisco Systems Inc’s Webex Teams.