Convert OBJ to STL — Print-Ready, No Upload

About This Converter

OBJ is a plain-text format that can describe a whole model: vertex positions, texture coordinates, per-vertex normals, named objects and groups, and a pointer to a separate material file that in turn points at image textures. STL describes exactly one thing, the surface, as a list of triangles with three corners and a facing direction each. That is the entire format. No materials, no texture coordinates, no colour, no names, no units. This direction is therefore a deliberate throwing-away, and it is worth knowing what goes. Materials and the material file they live in are dropped, texture coordinates are dropped, and per-vertex normals are replaced by one normal per triangle. Separate objects and groups are merged: if your OBJ held a lid and a box as two named pieces, the STL holds a single triangle soup with both still in their correct relative positions. Faces that were quads or larger polygons are triangulated on the way in, because STL has no other option. What survives is precisely what a slicer or a CAM tool reads anyway, which is shape and placement. The output is binary rather than text STL, roughly fifty bytes per triangle, and it is usually a good deal smaller than the OBJ you started with; text coordinates are verbose, and dropping the material and texture references removes the rest. Two things to check before you commit the file to a machine. First, geometry that was fine for rendering is not automatically fine for printing. Holes, flipped faces and non-manifold edges pass through this conversion untouched, and it is your slicer that will complain about them later, so repair them in a mesh editor if the file is refused. Second, size. OBJ records no units and neither does STL, so the number in the file is just a number, and the preview here scales the model to fit the viewer. Set the real dimensions in your slicer or CAM software rather than assuming they travelled with the file. Binary STL is what Cura, PrusaSlicer, Bambu Studio, most CAM packages and most print services expect, and it is one of the formats Scene Editor imports. The conversion runs entirely in your browser, with nothing uploaded and no account needed.