We consider polygonal Wilson loops with null edges in conformal gauge theories.
We derive an OPE-like expansion when several successive lines of the polygon
are becoming aligned.
The limit corresponds to a collinear, or multicollinear, limit and we explain the
of all the subleading corrections, going beyond the leading terms that were
These subleading corrections are governed by excitations of high spin operators,
of a flux tube that goes between two Wilson lines. The discussion is valid for any
theory, for any coupling and in any dimension.
For N=4 super Yang Mills we check this expansion at strong coupling and at
two loops at weak coupling .
We also make predictions for the remainder function at higher loops.
We will also discuss aspects of the excitations around the relevant flux tube or
"sea of derivatives''