The invention relates to a composite film (100) for packaging containers (1), having a film composite made of a plurality of packaging material layers (101 to 108), wherein an inner packaging material layer (108) is designed as a heat-sealing layer and an opening device (10) can be fixed to an outer packaging material layer (101), in particular by sealing to the outer packaging material layer (101), and wherein the packaging material layers (101 to 108) comprise a weakening region (20) in the region of the opening device (10). According to the invention, the weak region (20) is disposed on the side of the inner packaging material layer (108) and is implemented as an at least partial reduction in the layer thickness (D) of the inner packaging material layer (108), wherein the shape of the weak region (20), in particular having a circular cross section, is adapted to the arrangement of cutters (13) that are disposed on a partial circular diameter (T) of the opening device (10) as a part of the opening device (10).