Convert STL to OBJ
Free STL to OBJ converter that runs in your browser. See real dimensions before you download.
Why convert STL to OBJ?
People convert STL to OBJ to take a printable model into a program built for artists: Blender, Maya, a game engine, a renderer or a texturing tool. OBJ is plain, widely supported and easy to import almost anywhere. The conversion is straightforward because OBJ can hold any triangle mesh, but STL gives it very little to work with. There are no UVs, normals are derived from the triangle winding, and every triangle has its own duplicated vertices in many STL files. MeshShift welds identical vertices where it can, which gives a mesh that is easier to edit and smooth-shade. The output is geometry only; there is no MTL material and no texture.
How to convert STL to OBJ
- Drop your STL file onto the converter — it opens in your browser, nothing is uploaded.
- Check the preview and the dimensions in mm; fix units or the up axis in “Units & orientation” if the size or orientation looks wrong.
- Choose OBJ as the output and click Convert. Several files download as one ZIP.
What carries over from STL to OBJ
| STL | OBJ | Result | |
|---|---|---|---|
| Colour / materials | No | Yes | — |
| Textures | No | Yes | — |
| Units stored in file | No | No | Numbers in mm |
| Separate parts | No | Yes | — |
| Usual up axis | Z | Y | Rotated (switchable) |
What changes
- No UV coordinates or textures are created; you will need to unwrap the model yourself for texturing.
- Duplicate vertices from the STL are merged so the mesh can be edited and smooth-shaded.
- Everything is written as one object; STL had no part names to preserve.
- Millimetres are kept as the working unit; set the import scale in Blender if you want metres.
Tips
- In Blender, set the scene unit scale to 0.001 or scale the import by 0.001 so a 50 mm part is 0.05 m.
- Scanned or sculpted STLs are dense; use a decimate modifier before animating or rendering many copies.
- Flat shading will look faceted on low-poly STLs; shade smooth and, if needed, add an edge-split by angle.
About STL files
STL was created by 3D Systems in the late 1980s for its stereolithography machines, and it became the default exchange format for 3D printing. A file describes a surface as a list of triangles, each with three vertices and a facet normal. That is all it contains. There is no header field for units, no colour, no texture and no notion of separate parts. Two flavours exist: ASCII, which is readable text but large, and binary, which spends exactly 50 bytes per triangle after an 80-byte header and a 4-byte triangle count. Binary is what almost every modern tool writes. Because the format is so small and so old, every slicer, CAD package and mesh editor can read it, which is why hobbyists still download most printable models as STL from sites like Printables and Thingiverse.
About OBJ files
OBJ comes from Wavefront Technologies' Advanced Visualizer software in the 1980s, and it has outlived the product. A file is plain text: lines starting with v define vertices, vt texture coordinates, vn normals, and f faces that reference those lists by index. Faces may be triangles, quads or larger polygons, and the g and o keywords group faces into named objects. Appearance is not in the OBJ at all; a line called mtllib points to a separate .mtl file that lists materials with diffuse colours and texture image names. The format is verbose, has no official unit and no scene hierarchy or animation, but it is trivial to read and write. That is why scanners, photogrammetry tools, sculpting programs and game pipelines still use it to move static meshes around.
3D printing notes
STL is still the safest file to hand to a slicer. Bambu Studio, PrusaSlicer, OrcaSlicer, Cura and the resin tools Chitubox and Lychee all import it, and they all treat the numbers as millimetres. The usual problems are scale (a model exported from a metre-based tool arrives 1000 times too small) and meshes that are not watertight, which makes slicers fill or skip regions. MeshShift shows the real dimensions before you convert and can scale from metres automatically. Its print check lists holes, non-manifold edges and flipped normals, and one click rebuilds a closed solid at the same size. If you need colours or several plates in one file, use 3MF instead.
Frequently asked questions
Will the OBJ be smooth or faceted?
The geometry is identical to the STL. Whether it looks smooth depends on shading in your 3D program. Apply smooth shading there; the underlying triangles are not changed.
Can I texture the OBJ afterwards?
Yes, but you must create UV coordinates in Blender or another tool first. The converter does not generate UVs because an STL contains no information to base them on.
Is this STL to OBJ converter free and private?
Yes. The conversion runs in your browser with JavaScript and WebAssembly, so your STL file is never uploaded to a server. There is no sign-up, no watermark and no daily limit; very large files are limited only by your device's memory.