Optimizely vs Slack

Slack is a team collaboration tool co-founded by Stewart Butterfield, Eric Costello, Cal Henderson, and Serguei Mourachov. The company originally raised nearly $43 million in April 2014. In March 2015, Slack signed a deal with investors to raise up to $160 million in a funding round that values the company at $2.76 billion. New investors include Institutional Venture Partners, Horizons Ventures, Index Ventures and DST Global.