The song was released on May 15, 2017, by JYP Entertainment and distributed by KT Music, as the lead single from their fourth extended play of the same name.
[2][3][4] In June 2017, Twice released a compilation album titled #Twice which consists of ten songs including both Korean and Japanese-language versions of "Signal".
[1][10][11] Lyrically, it expresses a girl's frustration who keeps sending "signs and signal" to hint her feelings for a guy but is unnoticed.
[17] It has a science fiction-fantasy theme featuring a green-headed alien and the nine members of Twice with their own superpowers: Nayeon's superpower is time reversing, Jeongyeon's is time freezing, Momo's is super speed, Sana's is invisibility, Jihyo's is x-ray vision, Mina's is hypnosis, Dahyun's is self-duplication, Chaeyoung's is telekinesis, and Tzuyu's is super strength.
[19][20][21] "Signal" debuted at number 1 for two consecutive weeks and 4 on Gaon's Digital Chart and Billboard Japan Hot 100, respectively.
At the 2017 Mnet Asian Music Awards, "Signal" won Song of the Year and Best Dance Performance – Female Group.