The song was first teased on Twitter with Gomez teasing the song tweeting "1000 yo sé que piensas en mí y el corazón se te mueve...si tú quieres ir a 1000...". Camilo quote tweeted her tweet saying "999... yo estoy en 999!", further confirming the collaboration. They tweeted a pre-save link shortly after. The song was released on August 27, 2021.
The song described as a dreamy and rhythmic-pop song with ballad at its arrangement.[1][2] Where it composed in the key of C♯ Major, with a fast tempo of 150 beats per minute and runs for three minutes and 44 seconds.[3] Lyrically, its "about the beauty of true love".[2]
The official music video for "999" was released on the same day as the song on August 27, 2021. It was directed by Sophie Muller.[4]
Credits adopted from Tidal.[8]
- Selena Gomez — vocals, lyricist, composer
- Camilo — vocals, lyricist, composer, producer
- Édgar Barrera — vocal, lyricist, composer, producer
- A.C. — producer, guitar, programmer
- Vnsa — mix engineer
- Mick Raskin — mix engineer
- Kat Dahlia — background vocals
- John Hanes — engineer, mix engineer
- Nicholas Ramirez — engineer
- Natalia Ramirez — engineer, vocal producer
- Bart Schoudel — engineer, vocal producer
- Chris Gehringer — mastering engineer
- Serban Ghenea — mixer
- Sam Riback — production coordinator
- Aleen Keshishian — production coordinator
- John Janick — production coordinator
- Nir Seroussi — production coordinator
- Zack Morgenroth — production coordinator
- Benjamin Tischker — production coordinator
- Vanessa Angiuli — production coordinator
