An electrical connector includes a pair of opposite contact modules commonly sandwiching a grounding module therebetween in a transverse direction wherein each contact module includes two sided contacts on two sides of an insulator while the front mating sections and/or the bottom connecting sections of all the contacts are aligned in the same line. The contacts on each side of the insulator include a plurality of differential pair contacts and a plurality of grounding contacts alternately arranged with each other along the side face wherein the lengths of the pair of contacts in each differential pair essentially have the same length for reducing skewing effect by extending the body of the lower contact curvedly while keeping that of the upper contact essentially straight in each differential pair.