Corneal crosslinking (CXL) has been proposed as a new modality to stop progression of keratoconus or secondary corneal ectasia, aiming to prevent progressive visual loss and to delay or avoid corneal transplantation. The possibility of strengthening corneal tissue by means of a photochemical reaction of corneal collagen by the combined action of riboflavin and ultravioletA irradiation (UVA), radically modified the conservative management of progressive corneal ectasia. This is a review of the state of the art of CXL. The paper describes basic principles, advantages and limitations of different CXL techniques and possible future evolution of the procedure.