After the unexpected commercial and critical success of his previous album, Play (1999), Moby started to write songs for a follow-up during its supporting tour.

In December 2000, Moby finished his world tour in support of his previous studio album, Play (1999), which had lasted for 21 consecutive months.

[4] Prior to starting on 18, Moby had friends in New York City, Los Angeles, and London search through local record shops for albums that contained strong vocals that he could use to sample from and write songs based on them, a technique he had used for Play.

After 10 months Moby had sent 35 discs comprising over 140 songs, which promoted ideas of making 18 a triple album, but his friends and management advised against it.

[3] Moby named the album after the number of tracks that he put on it, and his fondness towards the idea of the title being easily translated and known as something different in other countries.

[7] Moby had written "Harbour" in 1984, at nineteen years of age; Sinéad O'Connor was surprised upon learning this, as she initially thought the song related to pre- and post-September 11 events.

[8] Stephen Thomas Erlewine of AllMusic gave the album four stars out of five, writing that, "Moby not only creates a shimmering, reflective mood from the outset, but [that] he sustains it throughout the 18 songs, as the album shifts from pop and soul songs to soaring instrumental stretches letting the sound deepen and change colors with each new track.