Slack is reportedly raising another $500 million - and Amazon, Google, and Microsoft might try to buy it

Slack, the wildly popular chat app for the workplace, is raising another $500 million at a $5 billion valuation, reports Recode's Kara Swisher. That's significantly higher than Slack's previous private valuation of $3.8 billion.

Swisher also reports that Slack's massive fundraising round has attracted interest in a potential acquisition from Amazon, Google, Salesforce, and Microsoft, though no formal offers have been made. Bloomberg originally reported Amazon's interest in a Slack acquisition, with a potential bid of $9 billion or more.

A Slack acquisition by Amazon would fit into the retailer's broader plans to take on Microsoft Office and Google Gsuite in the business productivity software space. Salesforce has made similar moves with its recent acquisition of Quip, a word processor.

Meanwhile, Microsoft and Google have Microsoft Teams and Google Hangouts Chat, their own take on the chat concept popularized by Slack.

Still, over the years, Slack CEO Stewart Butterfield has signaled repeatedly that he sees the company remaining independent. If Slack does hold any formal acquisition talks, it would signal a huge change in the company's thinking.

Slack did not immediately respond to a request for comment.

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