Cal Henderson

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Cal Henderson
Cal Henderson CC-BY.jpg
Born Callum James Henderson-Begg
17 January 1981 (1981-01-17) (age 36)
Nationality British
Occupation computer programmer, author

Callum James Henderson-Begg (born 17 January 1981), known as Cal Henderson, is a British computer programmer and author based in San Francisco. He was educated at Sharnbrook Upper School and Community College.[1]

He is best known for being the cofounder and CTO of Slack (software), as well as co-owning and developing the online creative community B3ta[2] with Denise Wilton and Rob Manuel; being the chief software architect for the photo-sharing application Flickr[3] (originally working for Ludicorp[4][5] and then Yahoo) and writing the book Building Scalable Web Sites[6] for O'Reilly Media. He has also worked for EMAP[6] and is responsible for writing City Creator[7] among many other websites, services and desktop applications. Cal was the co-founder and VP of engineering at Tiny Speck,[8] the company whose internal tool transitioned into Slack (software).

He is color blind, and has worked on applications to make the web more accessible to the color blind.[9] He is also a frequent contributor to open source software projects and runs a number of utility websites, such as Unicodey, to make certain programming tasks easier.


  1. ^ "Cal Henderson is the co-founder of the San Francisco-based Tiny Speck". June 2014.  |publisher= Sharnbrook Upper School
  2. ^ "Interview with B3ta co-founder Rob Manuel". BBC. August 2005. Retrieved 2007-06-12. 
  3. ^ "About Flickr". Flickr. Retrieved 2007-06-12. 
  4. ^ "The Ludicorp Team". Ludicorp. Archived from the original on 2007-06-10. Retrieved 2007-06-12. 
  5. ^ "The Team: Web Development Lead: Cal Henderson". Ludicorp. Archived from the original on 2004-02-11. 
  6. ^ a b "O'Reilly catalog - Building Scalable Web Sites". O'Reilly Media. Retrieved 2007-06-12. 
  7. ^ "City Creator - Yahoo! picks for September 16, 2003". Yahoo!. Retrieved 2007-06-12. 
  8. ^ "Companies > Tiny Speck". Crunchbase. 
  9. ^ Color Vision - by Cal Henderson

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