The Grammy Award-winning band performed its latest single "The Miracle (of Joey Ramone)" at the Cupertino, California event, at which Apple unveiled two new iPhones, a smart watch and a mobile payments system.
U2 released its new 11-track "Songs of Innocence" live on stage with Apple Chief Executive Officer Tim Cook. The album immediately appeared in iTunes users' music libraries.
However, the giveaway to more than 500 million iTunes users will not count toward official music sales figures at Nielsen SoundScan because it was distributed for free.
The band will release "Songs of Innocence" and a deluxe version featuring four new tracks and acoustic performances to the rest of the world on Oct. 14, its label Interscope Records, said on Tuesday.
Billboard, which will include the album in chart listings only after its October release, said on Tuesday that "Songs of Innocence" will also miss the Grammy awards eligibility period, which runs from Oct. 1 2013 to Sept. 30 this year, and only applies to "commercially released" records.
In July 2013, rapper Jay Z released his album "Magna Carta Holy Grail" for free to a million users of Samsung smartphones via a special app. However, the 1 million copies were not eligible for Nielsen or Billboard's weekly charts of best-selling albums.