Synthetic jets with circular and fractal orifices are experimentally investigated using time-resolved stereoscopic particle image velocimetry. The synthetic jet with circular orifice exhibit more rapid centreline velocity decay and half-width growth, indicating superior entrainment over the continuous jet. The synthetic jets with fractal orifices show intermediate entrainment performance between the round synthetic jet and continuous jet. The analysis on turbulent/non-turbulent interface (TNTI) properties reveals that the fractal orifice reduces the mean value and fluctuation of the radial position of the TNTI, as well as the tortuosity of the TNTI. This reduction in TNTI properties leads to a decrease in the area where nibbling occur. Consequently, synthetic jets with fractal orifices exhibit inferior entrainment performance compared to those with circular orifices.