Songfacts®:

• This is the first single from the dance-pop act Selena Gomez & The Scene's third album. The song was debuted on the March 10, 2011 On Air with Ryan Seacrest show on 102.7 KIIS FM. The digital single was made available four days later on March 14th.
• The uptempo paean of self-empowerment was co-written by Priscilla Renea (Cheryl Cole, Rihanna) and the track's producer, Eman (Whitney Houston, Celine Dion). Priscilla Renea started using the name Muni Long in 2019 and had her own hit with "Hrs And Hrs" in 2022.
• Chris Applebaum, who has directed videos for Rihanna, Britney Spears, and Mariah Carey, helmed this song's music video.
• Selena explained the song's meaning during its preview on Ryan Seacrest's show. Said the Wizards of Waverly Place actress: "When I heard it, I felt like my fans need this song right now, especially with Twitter and Facebook. I feel like it's really negative for me. Within that world, there's just such easy access to people's feelings. This song is such a great message to my fans, and it really touched me when I heard it."
  
  She added: "Basically, it's to the haters, it's to the people who try to bring you down."
• Selena explained to E! what the message of the song is for her: "I feel that girls my age tend to question themselves a lot. They tend to dress and be what other people want them to be. I feel that everyone wants to follow the trends and what's 'cool' and eventually, at the end of the day when you strip all of that down, are you really proud of yourself and comfortable in your skin?"
• After her sophomore album, A Year Without Rain, came out in September 2010, Selena wasn't planning on releasing anything else for a time, but this song altered her plans. "The original layout of my album was, I wasn't going to release one for a while," she told MTV News. "But I heard 'Who Says,' and I thought it was amazing, and it completely inspired me.
  
  I felt like my fans need this song right now," Selena added. "So I thought it was a sweet message. With bullying, with cyberbullying, with all the negativity that is in high school and dealing with things, you're already trying to figure out who you are; it doesn't help when people are constantly trying to tear you down. And I'm dealing with it, of course. I'm going through it as well."
• When The Sun Goes Down also contains a Spanish language version of the song, called "Dices." Selena explained to Billboard magazine: "'Dices' is 'Who Says' in Spanish. We actually recorded that because I recorded 'A Year Without Rain' in Spanish and it did really well and I love being able to connect with that side of me. I'm not fluent in Spanish so it's nice to sing it and makes my family proud. I love being able to sing in Spanish and I hope I eventually get to record more of that and maybe release an album in Spanish one day. We put it on the album because we did it in the second album and it's just kind of a nice little extra."