Office collaboration superstar Slack said Tuesday it accepted another US$427 million in funding to scale its business as it competes with enterprise technology heavyweights in a rapidly expanding market.
The latest infusion through a Series H round gives Slack a valuation north of US$7.1 billion, making the four-year-old company one of the most valuable startups in the industry.
Dragoneer Investment Group and General Atlantic led the latest round, which brought Slack's total funding to more than US$1.26 billion.
Slack has seen remarkable enterprise penetration over the past few years, becoming an ubiquitous communication tool among office workers at a who's who of corporate giants.
At the same time, the market the US-based startup helped pioneer is being challenged by tech giants who are building competitive products into prominent office productivity suites.
Slack hasn't been sitting idle.
Last month, the startup inked a deal with Atlassian, developer of rival platforms Hipchat and Stride, that will rapidly swell Slack's user base.
Slack purchased the intellectual property behind Atlassian's two messaging products with the aim of shutting down those services and partnering with Atlassian to migrate users to its own platform. Through the deal, Atlassian took a small stake in Slack.
"We pursued this additional investment to give us even more resources and flexibility to better serve our customers, evolve our business, and take advantage of the massive opportunity in front of us," Slack said in a blog post about the latest round.
Slack said it has more than 8 million daily active users, with more than 70,000 paying customers.
"There is still enormous potential to change the way that people and organisations collaborate and work together," the company said.