Kevin Christopher Bollaert, 27, entered his plea in court in San Diego, Karen Dalton told AFP yesterday.
He has been charged with 31 counts of conspiracy, identity theft and extortion over the racket, which allegedly earned him tens of thousands of dollars.
Judge David Szumowski set a preliminary hearing for March 17.
His lawyer did not immediately respond to a request for comment.
Bollaert, who is free on USD 50,000 bail, was arrested last month.
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The photos, commonly known as revenge porn, are typically obtained consensually during a relationship but then posted without permission, or are simply stolen or hacked.
Unlike other revenge porn websites where photos are anonymous, ugotposted.Com required the poster to include the subject's full name, location, age and Facebook profile link.
Bollaert created a second website, changemyreputation.Com, which he used when individuals contacted ugotposted.Com asking for their photos to be removed from the site.
"Online predators that profit from the extortion of private photos will be investigated and prosecuted for this reprehensible and illegal internet activity," Harris said in a statement in December.
In October, California Governor Jerry Brown signed a law banning revenge porn.