Slack's valuation tops $7.1 billion as venture investors keep piling into the messaging app

Key Points
  • Slack has now raised more than $1.26 billion in funding.
  • The business messaging app has more than 3 million paying users.
Stewart Butterfield, co-founder of Slack and Flickr
Mark Neuling | CNBC

Slack, maker of the popular business messaging app, is now worth more than $7.1 billion.

The San Francisco-based company said on Tuesday that it closed a $427 million funding round, padding its balance sheet as it takes on some of the world's biggest tech companies, including Google, Microsoft and Cisco.

Slack is among the most highly valued tech start-ups, and like consumer companies Uber, Airbnb and Pinterest, it has no plans to go public until at least 2019. Slack, which launched in 2014 and was valued at $5.1 billion almost a year ago, said it's bringing in more capital to go after growth. 

"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," the company said in a blog post.

More than 8 million people use Slack every day, and the service has over 3 million paying subscribers. Customers include Autodesk, Capital One, IBM and Target. Last year Slack had $200 million in annualized recurring revenue.

Atlassian was a competitor to Slack with its Hipchat Cloud and Stride services. But in July, Atlassian sold the intellectual property for those products to Slack and took an equity stake in the company.

To date Slack has raised more than $1.26 billion in funding. The newest funding round was led by Dragoneer and General Atlantic, and included participation from T. Rowe Price, Wellington Management, Baillie Gifford and Sands Capital.

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