“I Didn’t Change My Number” is the second track of Billie Eilish’s sophomore studio album, Happier Than Ever. On the song, Eilish sings about a past relationship and separating herself from this person. The song contains numerous samples of growls and barks from Eilish’s pitbull, “Shark”, a detail which was hinted at by Eilish’s brother/producer FINNEAS prior to the album’s release.

Prior to the song’s release, two lines of the song’s chorus were displayed on several articles of clothing from Eilish’s merch store.