"Bad Blood" is a song by the American singer-songwriter Taylor Swift from her fifth studio album, 1989 (2014). Swift wrote the song with the producers Max Martin and Shellback, and it is a pop song with stomping drums and keyboards. The lyrics are about betrayal by a close friend; many media publications interpreted that the American singer Katy Perry was the subject. A remix featuring the American rapper Kendrick Lamar, with additional lyrics by Lamar and production by Ilya, was released to radio as the fourth single to promote 1989 on May 17, 2015, by Big Machine and Republic Records.