Free online OBJ to STL converter

You keep the entire printable shape: the visible surface, triangulated faces, and object transforms all come through, converted locally in your browser and written as a compact binary STL. What you lose is everything STL cannot hold — texture images, MTL material assignments, object names, UV maps, smoothing groups, and separate OBJ groups. None of that affects your print: a slicer reads only the surface. One thing to watch is scale. If your OBJ was modeled in centimeters, millimeters, inches, or an arbitrary Blender unit, the STL carries the same numeric coordinates but not the unit label — so check the model's size in your slicer before printing, especially for exports from CAD or sculpting tools with different unit defaults.

Your converted STL has exactly the geometry your OBJ had — including its problems. Conversion is a format change, not a repair: non-manifold edges, flipped normals, paper-thin walls, and intersecting parts pass straight through. A printable file needs a closed surface with reasonable triangle density and no accidental internal shells, so if your slicer complains after converting, run the file through an STL repair tool rather than converting again. Also expect quads and n-gons to come out as triangles — a very dense sculpted mesh can produce a large STL that loads slowly in slicers and can hide detail finer than your nozzle or resin pixel size can reproduce anyway.

You want STL when your next stop is a slicer: it is the standard 3D printing handoff format, right for slicing, estimating print time, and sharing a geometry-only printable file. Keep the original OBJ if you plan to edit materials, separate parts, or adjust texture coordinates later — you can convert OBJ to STL again once the model is print-ready. And if what you actually need is a brand-new object rather than a format change, PrintReady3D can generate a custom 3D model from an image or text prompt and export a print-focused STL workflow.