Orbit is a versatile image analysis software for biological image-based quantification using machine learning, especially for whole slide imaging. Orbit has many built-in image analysis algorithms. Tissue quantification using machine learning techniques, object / cell segmentation, and object classification are the basic ones. Region of interest (ROI) can be defined by manual annotations or via a trainable exclusion map. Everything can be combined. All algorithms are built to work on really big images, up to gigapixel images, especially whole slide scans.