The group is under a 17-month contract; 5 months of training before promoting for 12 months.
Pre-debut: Under Nineteen
On April 5, the debut timeline started and the name of the album was revealed to be XIX with the title track being "Spotlight". A pre-debut title track, "Domino", which was written and produced by Under Nineteen's vocal trainer Crush, was released on April 7. The group then made their official debut on April 13 with the release of their debut mini album XIX.
On April 17, they held their debut showcase through V Live, with their fandom and fandom color announced to be Wonderland and Lime Punch, respectively.
|Jeon Do Yum (전도염)||Main dancer, lead rapper, vocalist, center|
|Jung Jin Sung (정진성)||Main dancer, lead vocalist, visual|
|Kim Tae Woo (김태우)||Vocalist, rapper|
|Shin Ye Chan (신예찬)||Main vocalist, lead dancer|
|Jeong Taek Hyeon (정택현)||Main rapper, vocalist, face of the group|
|Yoo Yong Ha (유용하)||Leader, lead rapper, vocalist|
|Park Sung Won (박성원)||Main rapper, vocalist, maknae|
|Lee Seung Hwan (이승환)||Lead dancer, lead vocalist|
|Kim Jun Seo (김준서)||Lead vocalist, lead dancer, rapper, visual|
- "Domino" (2019)