Open source map design studio for creating and styling web tile maps, based on either provided free MapBox Geodata, or data imported as a variety of file formats. It uses the CartoCSS styling language to customize interactive visualizations, with powerful control of symbols, zoom levels, labels, and other cartographic details. The finished maps can be exported either as images or tiled web maps. Though the TileMill software is free, there may be a fee to host the created tiles on MapBox or elsewhere.