What makes a track DJ friendly?

[Gymnor]

I have much experience with live bands, but recently discovered that beat makers apparently have a radio edit (which I knew) and a DJ friendly version. Which I knew as well, but it never occured to me that it is not just a "full" version. It's specifically tailored to suit the needs of a DJ.

Which prompted the question : What exactly makes a track DJ friendly, regardless the style of music you play?

 

[FlameOnTheBeat]

as far I understand, they just have an extra couple bars at the beginning and end so it's easier to switch songs.