As early as October 2018, rumors began circulating of JYP Entertainment's plans to debut a new girl group in 2019. Prior to their official reveal, in December 2018, fans uncovered JYP's new trademark for under the name "ITZY", speculating that this was the new group's name, and in January 2019 uncovered a JYP fan-catered website under the same name as well as potential social media accounts. The agency confirmed on January 14th that their the new group had filmed their music video but that the debut date was currently unconfirmed.

ITZY was official revealed on January 21, 2019 with a YouTube video titled "PROLOGUE FILM : ITZY? ITZY!". The video revealed the five members of the group, Yeji, Lia, Ryujin, Chaeryeong, and Yuna, and the group's official website and social media accounts. This was followed by multiple sets of image teasers and video teasers leading up to their debut.

On January 24, JYPE revealed the group will debut with the single "IT'z Different". On February 11, a music video teaser for the single's title track, "Dalla Dalla", was released. The music video was released on February 11 and the single on the 12th. The group held their live premiere the same day as the single's release.

On July 8, ITZY's fans gained a name: MIDZY. The name was revealed by the group's social medias, almost 5 months after their debut.