Chiefly written and sung by The xx's Oiver Sim, this song details his efforts to resist repeating his parents' mistakes and break away from his self-destructive behavior. Sim started writing the song after the band's 2012 tour had finished. He explained to The Guardian that living back in London again, at first he thought of his drinking and drug-taking as "blowing off steam". However, after a time he, "started to wonder if it was still charming to be the drunkest person in a room".
Eventually, Sim decided to seek help and when the band regathered to write their third album, he brought them the lyrics to "Replica." Co-vocalist Romy Madley Croft recalled the moment. "I thought: 'This is very real.' Even though everything we do is real, this felt more – transparent? It felt brave. And I loved that he let me in, to discuss it."