Free online tool to automatically extract closed boundary polylines, calculate area and perimeter, and add hatches to AutoCAD DXF files. Includes a built-in browser DXF viewer to preview drawings before and after processing with full color and layer support, plus pan, zoom, and pinch-to-zoom. Two algorithms: exact topological face extraction and approximate floor balayage for messy drawings. Automate quantity takeoff, room detection, and CAD area calculation.