The ballad[1] was released on 19 April 1999 in the United Kingdom as the first single from their self-titled debut album (1999).

[3] "Swear It Again" is notable for being, along with "Flying Without Wings", one of the first two songs that Steve Mac wrote for both Westlife and Simon Cowell.

The song's B-side, "Forever", was a significant choice because, as originally recorded by Damage, it first alerted Cowell to the talent of Steve Mac and then led to the producer working with Westlife.

[4] It was composed in the traditional verse–chorus form in A major, with Filan and Feehily's vocal ranging from the chords of B3 to F♯5.

[5] An exclusive live track version of the single was included in the Arista Records 25th anniversary compilation album in 2000.