Songfacts®:

• Selena Gomez's first new song since 2015 is a collaboration with Norwegian DJ Kygo. The pair penned the tune with former California Breed guitarist Andrew Wotman, Korean-American songwriter Brian Lee (Fifth Harmony's "Work from Home") and Ali Tamposi (Kelly Clarkson's "What Doesn't Kill You (Stronger)").
  
  Wotman, Lee and Tamposi also worked together on the DJ Snake and Justin Bieber track " Let Me Love You." Interestingly Bieber's lyrics for that song were rumored to be about his ex-girlfriend, one Selena Gomez.
• The song finds Gomez having lost patience with her lover staying out drinking all night.
  
  Who's gonna walk you through the dark side of the morning?
  Who's gonna rock you when the sun won't let you sleep?
  Who's waking up to drive you home when you're drunk and all alone?
  Who's gonna walk you through the dark side of the morning?
  It ain't me
  
  Gomez used to be there for her boyfriend but she's had enough of his drinking ways. Next time he arrives home hungover, she will have moved out.
• It has been suggested that the lyrics are about Justin Bieber but elsewhere in the song Selena talks about being "seventeen" and she was 18 years old when the pair started dating.
• Andrew Wotman, Brian Lee and Ali Tamposi had just spent a few months in London writing for Rita Ora when they got the call that Kygo was interested in collaborating. The trio started jamming and 45 minutes later, the "It Ain't Me" demo was written and recorded.
  
  "I feel the most proud of this song," Tamposi told Billboard magazine of the track. "If every song was that easy, I think I would be in less shock, but I'm in shock because it came together so perfectly. I can't imagine it being different in any way."
• Tamposi said that Gomez was quick to understand the song's emotional vision. "Society puts – especially for a woman – pressures that we have to be in a relationship in order to feel validated," she said. "[You're supposed to] stand by your man, even when he's bogging you down. When he's drunk, you've gotta pick him up and all these things. It takes a lot of strength to walk out of something."
  
  "[Gomez is] in a place right now where she feels like she can be the most honest and take a stand," Tamposi added. "She can utilize her platform and her voice and strength."
• Wotman told Billboard magazine the song "is about a girl's perspective looking at my life; she's not going to put up with my s--t anymore."
• The song was also included as bonus track on the Target edition on Selena Gomez' 2020 Rare album.