Police found Kroll, 34, unconscious and unresponsive in a bedroom of his Manhattan apartment, a New York police spokesman told NBC television.
A drug overdose is the suspected cause of death, police said, and an investigation is underway.
Kroll co-founded Vine, the popular short-form video service acquired in 2012 by Twitter that is now defunct.
In September, he was named the chief e
xecutive of HQ Trivia, a smartphone-based trivia platform.
HQ Trivia confirmed his death in a statement.
“We learned today of the passing of our friend and founder, Colin Kroll, and it’s with deep sadness that we say goodbye,” it said. “Our thoughts go out to his family, friends and loved ones during this incredibly difficult time.”
HQ Trivia, launched in August 2017, was a blockbuster, hitting a March milestone of two million concurrent players.
But by November, the number of users plunged from millions to hundreds of thousands, according to tech news site Recode.
Time magazine said Kroll, who was reportedly fired from Twitter over poor management behavior, was facing allegations he had acted inappropriately at HQ Trivia.