Now, he's worth more than $200 million.
But in an interview with Forbes' Jeff Bercovici, he says he that he doesn't recommend kids today drop out of high school.
"There's a lot that I feel like I missed out on," Karp tells Bercovici. "Just a whole lot of normal, social, childhood kind of stuff that I definitely missed out on."
Karp says that he dropped out because he knew exactly what he wanted to do: work with computers and do web development.
"If somebody else had that opportunity...well I wouldn't not encourage them to take it, I don't know that I'd be the one rooting for them to drop out of school."
Check out the video interview below. Karp starts talking about kids dropping out of high school around the 2:23 mark.