Confirming earlier reports, Slack Technologies just raised $200 million at a valuation of $3.8 billion. New investors include Thrive Capital, Comcast Ventures and GGV.
The popular messaging startup has already raised $340 million from Index Ventures, Andreessen Horowitz and Accel Partners, among others.
Slack has established itself as a company to watch in the white-hot mobile messaging space. Since the spring, the start-up has more than doubled its daily active users to 2 million and nearly tripled its subscriber base to about 570,000.
Standing apart from rival messaging services -- namely Facebook -- Slack has convinced subscribers to fork over monthly fees for premium features.
Late last year, Slack Technologies started an $80 million venture fund to support the creation of apps and add-ons that complement its business-focused group-messaging service.
The fund has already invested in Awesome -- a tool that organizes Slack activity -- along with a productivity software maker and a toolkit for building chat bots.
Slack is financing more than half of the total fund, while the remainder should come from its existing backers, including Accel Partners and Andreessen Horowitz.
To further encourage a complementary ecosystem, Slack is also readying the release of an app directory to show users how they can integrate apps into their chat rooms.
At last count, there were about 150 such applications.
Complicating Slack’s expansion plans, Facebook recently rolled out “Work Chat” -- a new messaging app designed specifically for business teams. Between its WhatsApp unit and Facebook Messenger, Facebook already dominates the mobile messaging space.
But, Slack seems determined to change that. Vying for a bigger piece of the group-messaging marketplace, it recently began rolling out a conference-calling feature named Calls.
Calls has been in the works since Slack picked up Screenhero for an undisclosed sum, in January. Technically still in beta, Calls boasts some novel features, including a simple emoji-reaction system.
Additional investors include Digital Sky Technologies, Horizons Ventures, Institutional Venture Partners, Spark Capital Growth, Google Ventures, Kleiner Perkins Caufield & Byers and Social Capital.Earlier reports put Slack's desired valuation as high as $5 billion.