Abstract: A web width control apparatus for controlling the ratio between web width change and web thickness change during a web length varying operation in a web transport system of the type including a moving web of relatively extensible maerial having a series of repeat length portions therealong which are designed to be presented at a web processing station at a preselected constant design length value and in which each said repeat length portion is subject to stretching or shrinking in length depending upon the tension provided in the region of the web in which said repeat length portion is positioned; and further including a first set of nip rolls operable at a selected surface velocity and a second set of nip rolls operable at a selectively variable surface velocity with respect to the surface velocity of said first set of rolls for causing relative length change in a web portion positioned therebetween for adjustably maintaining the respect length portions of the web at said predetermined design length value at