WITOIL (Where Is The Oil) is a service provided for prediction of transport and transformation of actual or hypothetical oil spills in the Mediterranean Sea.

As an interactive system, WITOIL requires the input of data for atmospheric wind, sea surface temperature, and sea currents. The atmospheric wind data are provided by the European Centre for Medium-Range Weather Forecasts (ECMWF), at 0.125 horizontal and 6-h temporal resolution. The ocean current data are provided by hourly forecast fields produced by the Mediterranean Forecasting System (MFS) at 1/16 ° horizontal resolution.

WITOIL provides users with the spatial-temporal distributions of oil concentration at the sea surface and coastline, and the components of oil mass balance. WITOIL output consists of graphics and animations available through web browser.