Martin Garrix surprised fans by debuting "Fireflies," his previously unheard collaboration with U2, during his headlining set at Tomorrowland in Boom, Belgium, on Friday 17 July. U2 guitarist The Edge joined the Dutch DJ on stage to play the track live, while Bono's vocals featured on the recording, marking the song's live premiere ahead of its official release. The moment closed out the festival's opening night and underlined the enduring creative partnership between the electronic dance star and the veteran Irish rock band.

The track, announced as "out soon" via Garrix's Instagram, is now available to pre-save on Spotify and Apple Music, though it remains unclear whether it will feature on a forthcoming album from either act. Garrix and U2 have collaborated before, notably on "We Are the People," the official UEFA Euro 2020 song, which reached number 12 on Billboard's Hot Dance/Electronic Songs chart, and Bono has co-written several Garrix tracks. The news also comes as U2 prepare their first studio album since 2017's Songs of Experience, having already released the single "Street of Dreams" and two surprise EPs earlier this year.