In May 2019, Russian trance producer Arty filed a lawsuit against Marshmello for copyright infringement, citing that "Happier" stole song elements from Arty's remix of the song "I Lived" by OneRepublic. According to the suit, it is possible that Marshmello had become familiar with Arty's remix, released in 2014, and had used song elements in his then-upcoming song "Happier," which did not debut until 2015. Alongside Marshmello, other defendants in the case include Dan Smith, Steve Mac, and various music publishing companies. Arty is represented by attorney Richard Busch, who had previously represented the Marvin Gaye family in the "Blurred Lines" suit.
