Coldplay watch their crowds during their concerts to see which songs they are enjoying so they can refine their set list.
Coldplay consider fans' toilet breaks when choosing their set list.
The 'Fix You' hitmakers constantly watch their audiences during concerts and if they see people getting restless during certain songs, they axe the track from subsequent shows.
Frontman Chris Martin explained: "In some songs all you can see is a clear doorway and you can hear the crowd singing so you think, 'Wonderful, this song is great.'
"And then it's when the light all starts getting blocked and everyone's going to the bathroom. Then you're like, 'OK, that song's out.' "
The quartet are now regarded as one of the world's biggest bands, but they almost split up months after they first signed their record deal.
Drummer Will Champion was thrown out of the band after he was blamed for a producer's accusations they weren't "good enough" to succeed.
However, Chris admitted on upcoming UK TV documentary 'The South Bank Show' that he was rehired days later because "we felt really miserable without him."
Coldplay started the UK leg of their world tour last weekend and the singer admits the foursome - which is also comprised of guitarist Jonny Buckland and bassist Guy Berryman - were initially apprehensive about the reaction of their home fans.
Chris said recently: "It feels like we have been away for a long time. The four of us were feeling really nervous about coming back home."