The phase shift schlieren (PSS), an improved method of the conventional schlieren imaging technique, enables direct quantitative measurements of optical path length gradients. Like all phase-shifting imaging methods, a successive acquisition of multiple images is required, therefore limiting the PSS use to quasi-steady-state phenomena. We show that PSS can be easily modified to access real-time data. A possible implementation is disclosed, as well as experimental results that validate the method. An application on gas jet is illustrated. We present the features and limitations of the real-time phase shift schlieren (RTPSS).