Slack Valuation More Than Doubles to $2.8 Billion Slack Valuation More Than Doubles to $2.8 Billion The messaging app just raised $160 million in a new financing round.

By Ari Levy

This story originally appeared on CNBC

Slack

Six months ago, a year-old messaging app called Slack lit up the tech blogs when it raised money at a $1.2 billion valuation. Well, try $2.8 billion

That's how high investors including DST Global and Index Ventures are valuing the start-up, based on a $160 million financing round announced Thursday. All for a service that's effectively trying to kill internal e-mail use by simplifying communication among teams.

Created by Flickr co-founder Stewart Butterfield, the San Francisco-based company has over 200,000 paid users, and 750,000 people access the service daily. Customers include Adobe, the New York Times, HBO and Expedia.

"Stewart and the team at Slack have taken a page out of the consumer playbook and revolutionized business communications by taking a generationally-different approach to messaging," said Mike Volpi, partner at Index Ventures and now a Slack board member, in the statement.

Slack didn't specify how it's going to put all this fresh cash to work, just months after raising $120 million. The biggest challenge is creating staying power in a market where many companies have emerged then fizzled. And there's competition from Atlassian's HipChat service as well as Asana and Basecamp.

"We're still at the beginning of a major transition in how people communicate and work together," said Butterfield.

The investing round was joined by all existing backers, including Andreessen Horowitz, Kleiner Perkins Caufield & Byers and Google Ventures.

Ari Levy is CNBC's senior technology reporter in San Francisco.

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