In August 2017, JYP Entertainment (JYPE) officially announced the agency’s new reality survival show to launch a male idol debut project. More details and teasers were released in the next two months, including the show’s title—Stray Kids. Prior to its premiere, JYPE released Stray Kids’ first music video for a song titled “Hellevator”, which was later released as a digital single. The show premiered on October 17 and had eliminations. The first who was eliminated was Lee Know and the second was Felix, however all nine members ended up in the final line-up of the group.
Along with the launch of Stray Kids’ official website, JYPE announced the release of the group’s pre-debut extended play (EP) titled Mixtape. It contains seven tracks co-written and co-composed by the members, including “Hellevator” and other songs that they performed during the show. The EP, along with the performance video of its second track titled “Beware”, was released on January 8, 2018, while the performance video of “Spread My Wings” was uploaded online a week later. It debuted at number 2 on Gaon’s Album Chart and Billboard‘s World Albums chart.
On March 5, JYPE announced the debut showcase of the group titled Stray Kids Unveil (Op. 01: I Am Not), which was held on March 25 at Jangchung Arena. They officially debuted the next day with the release of their EP titled I Am Not, along with the music video of its title track titled “District 9”, while the music video of “Grow Up” and performance video of “Mirror” were released on March 31 and April 23 respectively. I Am Not debuted at number four on Gaon’s Album Chart and sold over 54,000 physical copies in March.
On April 14, Stray Kids performed at KCON Japan 2018, the group’s first overseas performance since debut.