ShapeOut is the analysis software for real-time deformability cytometry (RT-DC), a technique developed in our lab and commercialized by the spin-off company ZELLMECHANIK DRESDEN GmbH. In contrast to standard cytometry techniques, RT-DC records image data and analyzes several cell parameters such as size, shape, or deformation, which requires a novel analysis pipeline that ShapeOut provides. Each event in a scatter plot represents a measured cell and can be selected to get additional information such as its image and the computed contour. All data recorded during the measurement (e.g. cell images, fluorescence traces, etc.) are available to the user and can be used for filtering and visualization.