This song features on the soundtrack of the romantic comedy-drama movie The Fault in Our Stars. "The scene that ['Boom Clap'] is in is an uplifting moment in the film," XCX explained to Billboard magazine. "And while the song itself is very euphoric and enthusiastic about romance… it's about wanting to fall in love, but there's this hint of sadness in that, which I like."

Charli and Patrick Berger wrote this song in Stockholm. She explained the inspiration to Entertainment Weekly: "We had been listening to loads of French yé-yé pop and the Flying Lizards and Bow Wow Wow, and we were saying how all those songs have dumb, hooky, shouty choruses. They're all sort of childlike. So we wanted to make a song like that.

The song celebrates epic love. "Being totally immersed in passion and feeling really safe and really alone with that person," Charli explained to MTV UK. "Although I always hear a tinge of sadness in it, that song has quite an acute feeling."

The Sing J. Lee-directed video features Charli XCX traipsing through the Amsterdam city. The singer explores the same spots that were featured in The Fault in Our Stars movie.

Charli XCX wrote the song during the sessions that produced the tracks for her debut album True Romance. She penned the tune with Patrick Berger, her collaborator on "I Love It." It didn't make the final cut and was then offered to Hilary Duff to record.

XCX told MTV UK that Berger has worked with Hilary Duff before, and when the singer's people got in touch with them about her new record, she got very excited. "My number one project as a songwriter is to write for Hilary Duff, so when I heard about this, I was like, 'f---k! Are you serious?! This is my 'in!,'" she recalled. "I'm going to make a Hilary Duff album!' So we sent over 'Boom Clap', but they came back and were like, 'this isn't cool enough for Hilary."

"I was like, crushed," Charli added, sighing. "I thought I was a cool writer, but maybe I'm not. Hilary didn't want my song. What a life-ruiner."

Once Duff declined the offer, XCX decided to use the song as her contribution for The Fault in Our Stars.

If you think this song has a dumb chorus, you're right - at least according to Charli. She says that it is dumb, but some of the best pop songs have one-line, catchy choruses.

Charli XCX recorded a version of both this song and "Break The Rules" in Japanese to promote the Japanese release of Sucker. "Boom Clap's" onomatopoeic title stayed the same, but the English words elsewhere were translated. "I did it phonetically," Charli recalled to Digital Spy. "I don't actually remember it now; it was more just me repeating the sounds. But I'm very happy with it, I've always been inspired by Japan constantly, so I kind of wanted to do something for the Japanese fans."