Slack now has 1.1 million active users and has reached $25 million in annual revenue.
The multi-billion-dollar startup, the fastest-growing ever, celebrated the milestones by hiring Google and Twitter alumnus April Underwood as head of platform.
According to PitchBook, Slack reached a valuation of $1 billion 1.25 years after launching, ahead of Groupon (1.46 years) and Akamai Technologies (1.58 years). Slack then reached a valuation of $2 billion just 1.71 years after launching, ahead of companies like Xiaomi Technology (2.24 years) and Instacart (2.58 years).
Slack CEO Stewart Butterfield founded Flickr in 2002, which he sold to Yahoo in 2005. He recently made headlines for a tweetstorm about racism and the Wall Street Journal.