Which U2 album was given free to iTunes users in September 2014?

Songs of Innocence was given free to iTunes users in September 2014.

U2 released Songs of Innocence on 9 September 2014 through an arrangement with Apple. The album was automatically placed in the iTunes libraries of many users, making it available at no charge to more than 500 million iTunes customers at the time. The unusual distribution method generated enormous visibility but also criticism from people who did not want the album added to their accounts.

The album explores the band members’ adolescence, family backgrounds and early musical experiences. Its title was inspired by William Blake’s collection Songs of Innocence and of Experience. The record was later issued through conventional digital, CD and vinyl formats.

Songs of Innocence was followed by Songs of Experience in 2017. The two titles are linked conceptually, but they are separate studio albums rather than two names for the same release.