WaveGen is a universal app on wind-wave prediction. The app calculates wind-generated waves based on user-specified wind observation data, fetch and storm durations. The calculation follows the approach outlined in Coastal Engineering Manual (CEM). Users need to ensure the observed wind speed is equivalent to "over water" wind speed. "Over land" wind speed needs to be converted to "over water" wind speed. The app outputs significant wave height, peak wave period, type of wave generation (fetch-limited, duration-limited, or fully developed).