Cal Henderson is the co-founder and CTO of Slack. He oversees Slack’s world-class engineering team and sets the technical vision for the company.

In 2019, he was named a Fortune 40 Under 40 honoree and recognized by the World Economic Forum as a Young Global Leader.

Previously, Cal built and led the engineering teams at Flickr, through its acquisition by Yahoo. An experienced technology leader and a popular speaker on engineering scalability, he authored the best-selling O’Reilly Media book Building Scalable Websites. Cal was also a pioneer in the use of web APIs, and created the basis for OAuth and oEmbed, now used by YouTube, Twitter and many others.

Cal was involved in London’s early online network through his work with digital creative communities and the blogosphere. He has a BS in Computer Science and has received an Honorary Doctorate from Birmingham City University. He now resides in San Francisco.