OBJ to STL Converter — Free, Browser-Side, No Upload
OBJ → STL
Convert OBJ files to STL format in your browser. Ideal for 3D printing. No file upload required. Supports single and multi-object OBJ files.
Use this when
- Audience
- 3D printing users searching for OBJ to STL when a slicer or print workflow needs STL geometry.
- Task
- Convert OBJ mesh geometry into a slicer-friendly STL while keeping the file local in the browser.
- Successful outcome
- Download the STL, import it into the slicer, and check scale, manifold status, and printability.
- Boundary
- This drops OBJ materials, textures, MTL data, object hierarchy, and unit metadata.
Best for
- Preparing OBJ mesh geometry for a 3D printing slicer
- Removing material dependencies when only printable geometry matters
- Turning a multi-object OBJ into one STL mesh for basic print workflows
- Converting locally when the model should not be uploaded to a cloud converter
Before you start
- Confirm the final size in your slicer because STL does not store units
- Do not expect textures, colors, or MTL materials in the STL output
- Repair or simplify broken OBJ geometry before converting if the file imports poorly
- Check overhangs, wall thickness, and manifold status in your slicer after download
Next steps
- Estimate the print costUse slicer grams and print time from the STL workflow to estimate baseline cost.
- Check why materials disappearedConfirm whether STL is the right output when textures or colors matter.
- Inspect or repair the STLUse this if the slicer warns about non-manifold edges, holes, or shells.
Known Limitations
- OBJExporter does not export MTL material files; geometry only, materials/textures are lost
- STL output has no units — confirm scale in your slicer after conversion
- STL output has no materials or textures
- STL stores triangles only; any quads in the OBJ will be triangulated
Helpful guides
- Why OBJ to STL loses materialsSee why colors, textures, and MTL data disappear.
- Why STL files have no unitsCheck scale assumptions before slicing the STL.
- OBJ vs STL for 3D printingUnderstand what is lost when OBJ becomes slicer-friendly STL.
- 3D file conversion loss matrixCheck geometry, material, texture, and unit loss.
Frequently Asked Questions
Will my OBJ textures and materials be kept in the STL output?
No. STL stores geometry only — it has no material, color, or texture fields. All material and texture information from the OBJ (and its MTL file) is dropped during conversion.
Can I convert a .obj file to .stl for 3D printing?
Yes. Upload the OBJ file in your browser, convert the mesh geometry to STL, and download the STL for your slicer. Check scale and printability afterward because STL has no units, no materials, and no object hierarchy.
Do I need to include the .mtl file alongside my .obj file?
No. The converter reads geometry from the OBJ file only. The MTL file is ignored because STL has no material support anyway.
Will the scale change after converting OBJ to STL?
The converter preserves raw coordinate values. However, STL has no unit metadata, so your slicer may interpret the numbers differently. Always confirm scale in PrusaSlicer or Cura after importing.
Does this work with multi-object OBJ files?
Yes. Multi-object OBJ files are supported. All geometry is merged into a single STL mesh on export, since STL has no object hierarchy.
Does my file get uploaded anywhere?
No. Conversion runs entirely in your browser using Three.js. Your file never leaves your device.
Related tools
How it works
Your files are processed entirely inside your browser using Three.js. Your files never leave your browser — there is no server upload, no cloud storage, and no third-party processing. The converted file is generated as a local Blob and downloaded directly to your device. Once the conversion is complete, all data is released from memory.