Emma Stone and cinematographer Linus Sandgren previously worked together on the film La La Land (2016) and Battle of the Sexes (2017), the former of which won them both Academy Awards.
Paul McCartney described the song being about bullying, stating, "With Who Cares, I was thinking about a song where you actually are talking to the people who may listen to it. And in my case I was imagining young fans, or young people who might hear this, and who are going through some sort of problem where they're being picked on, being put on. These days it would be internet bullying, trolls and all that. In my school days, it would have just been bullies and people just generally picking on each other. So I know that has happened all over the world to millions of people. So my thing was to kind of try and help, try and help, almost kind-of give some sort of advice. So the song says, you know: "have you ever been fed up with being bullied?" Has this ever happened when people have called you names, have done mean things? Has this ever happened to you? Well, who cares. And then in a twist at the end of that chorus is like "Who cares? I do"."
In departure from many of Paul McCartney's latter day recordings, "Who Cares" is performed by McCartney with his full live touring band of Rusty Anderson, Paul Wickens, Brian Ray, and Abe Laboriel Jr..