Frequently co-writing with Julia Michaels, Tranter has written songs for artists such as Britney Spears, Gwen Stefani, Linkin Park, Kelly Clarkson, Selena Gomez, Justin Bieber, DNCE, Kesha, Imagine Dragons, Fifth Harmony, 5 Seconds of Summer, Ariana Grande, Lady Gaga, Bea Miller, Demi Lovato, Dua Lipa, and Fall Out Boy. From 2004 to 2014, Tranter was the lead singer of Semi Precious Weapons, a rock band based in New York. Since February 2017, they have been a board member of GLAAD, an organization that promotes LGBT acceptance in the entertainment and news industries.