The CEO, who also co-founded the video platform Vine, was found by police after his girlfriend reportedly asked them to check on him.
An HQ spokesperson confirmed the death "with deep sadness".
HQ Trivia, a live trivia game on mobiles, became hugely popular, although its appeal waned this year.
Officers of the New York Police Department went to Mr Kroll's flat in Manhattan to carry out a welfare check and found his body along with drugs paraphernalia nearby, TMZ reported in the initial media coverage of his death.
The HQ statement read: "We learned today of the passing of our friend and founder, Colin Kroll, and it's with deep sadness that we say goodbye. Our thoughts go out to his family, friends and loved ones during this incredibly difficult time."