Founder Profile
Cal Henderson
Last reviewed: October 2026 · By Swet Parvadiya
Who is Cal Henderson?
Cal Henderson is a founder of Slack Technologies, LLC, which was founded in 2009 with Stewart Butterfield, Eric Costello and Serguei Mourachov.
- Company founded
- Slack Technologies, LLC
- Founded
- 2009
- Co-founders
- Stewart Butterfield, Eric Costello and Serguei Mourachov
Background
British software engineer and tech pioneer.
Founding Story
Cal Henderson co-founded Slack in 2009 (originally Tiny Speck). Before Slack, he co-founded Flickr alongside Stewart Butterfield. As an absolutely brilliant technical architect, he built the incredibly complex real-time messaging infrastructure capable of handling millions of concurrent enterprise users without dropping a single message, serving as CTO for over a decade. Cal Henderson was born in 1981.
Sources
This profile does not yet cite a source specific to Cal Henderson. The sources below document the company company rather than the person, so check them against the claims above.
- Slack Announces Strong Fourth Quarter and Fiscal Year 2021 Results (Slack Technologies, LLC)
- Slack Technologies SEC filings (EDGAR) (Slack Technologies, LLC)