STL ExtrudeLab is a light, browser-based tool that lets you extend and adapt existing 3D mesh models like STL, OBJ, and PLY. Downloaded a model that's almost perfect? Just extend it, select any surface, extrude it into pipes, channels, or angled extensions, right in your browser. No install. No CAD skills. No Blender rabbit hole. Just load your STL, pick a surface, drop some waypoints, and export print-ready in minutes. Free, offline-capable, files never leave your machine.