Browser-based conversion
Use the converter without installing desktop software to move from STL to OBJ.
Free under 5 MBSTL → OBJNo software installation
Convert STL
to OBJ online
Convert an STL (.stl) mesh into OBJ online. Upload your file in the browser and download the converted result without installing desktop CAD software.
Encrypted uploads Files up to 300 MB Deleted after 7 days
Upload your STL file
Choose one file to begin the conversion.
Drag and drop your 3D file here
or choose a file from your computer
Browse filesMaximum file size: 300 MB
Files under 5 MB convert and download free. Larger files require a small fee per conversion, including a new file or re-run.
Don't have a file? Try a sample:
Built for polygon mesh
Translate triangular surface mesh into the polygonal mesh used by OBJ.
Ready for the next workflow
Open the result in Blender, Maya and rendering tools for review, editing or production.
Private file handling
Converted models are not added to the public CAD library and are removed after processing.
Continue your CAD workflow
Explore Marathon
OS CAD resources
Preview a model before conversion, find an existing engineering file, open a 2D drawing, or get specialist help when a source mesh needs to be rebuilt.
Browse CAD modelsSearch ready-to-use engineering and 3D-printing files across the Marathon OS library.Browse 2D technical drawingsExplore PDF, SVG and DXF drawing resources for engineering review and documentation.Get CAD design supportWork with a vetted designer when the model needs repair, remodelling or a production-ready native file.
Simple conversion workflow
How to convert STL to OBJ online
Move from STL mesh to Wavefront OBJ in three clear steps.
Upload your STL file
Drag and drop the .stl file into the converter or choose it from your device. Files up to 300 MB are supported.
Use OBJ as the output
This page is preconfigured for STL-to-OBJ conversion, so you do not need to search through target formats.
Download and inspect the OBJ
Download the result and open it in your preferred compatible application to confirm its geometry and scale.
Format behaviour
What changes when
STL is converted to OBJ?
STL and OBJ describe geometry differently. Conversion preserves compatible shape and topology while translating or omitting format-specific data.
Normally retained
- Overall model shape
- Compatible geometry
- Model orientation
- Supported topology and layers
May not be retained
- Format-specific metadata
- Unsupported materials or textures
- Application-specific features
- Data without a target-format equivalent
STL meshSTLWavefront OBJOBJKeep the original STL file as the source of truth and inspect the converted OBJ file before downstream production use.
Format comparison
STL versus OBJ
Choose the output according to what the next stage of your workflow needs.
| Feature | STL STL | OBJ OBJ |
|---|---|---|
| Main purpose | 3D printing, slicing and rapid prototyping | 3D modelling, rendering and asset exchange |
| Geometry | Triangular surface mesh | Polygonal mesh |
| Textures and UV mapping | Not supported in standard STL | Supported through referenced assets |
| Materials | Not supported in standard STL | Can use an accompanying MTL file |
| Object groups | Does not retain named object groups | Can contain named objects and groups |
| Common workflow | Cura, PrusaSlicer and 3D printers | Blender, Maya and rendering tools |
Choose OBJ when
Your next application or supplier specifically requires a OBJ file.
3D modelling, rendering and asset exchange is the next stage of the workflow.
The target geometry representation suits the downstream task.
Keep STL when
Your project still depends on data unique to the source format.
You need to continue editing in Cura, PrusaSlicer and 3D printers.
The model is still being prepared rather than handed off.
Before continuing
Check the converted
OBJ before the next step
Changing the file format does not automatically make a model production-ready. Review these checks in the application used for your next workflow.
Important: File formats may not include a standard unit definition. Always verify dimensions after conversion.
- 01
Verify dimensions and scale
Confirm that the converted OBJ file uses the expected size and unit interpretation.
- 02
Inspect the complete geometry
Check that all expected bodies, surfaces, curves or drawing entities are present.
- 03
Review surface orientation
Look for flipped faces, inconsistent normals or reversed boundaries after conversion.
- 04
Check topology and open edges
Inspect gaps, overlaps, invalid edges and disconnected geometry before downstream use.
- 05
Confirm layers and object structure
Verify that supported layers, groups and model organisation were translated as expected.
- 06
Open the file in its target application
Preview the OBJ result in the software used for the next workflow before production use.
Common problems
STL-to-OBJ conversion troubleshooting
Most conversion issues come from differences between file formats or problems already present in the source geometry.
The OBJ file has the wrong size
The source and destination tools may interpret units differently. Open the OBJ file and select the correct unit or scale.
Fix: Verify units and dimensionsTextures or materials disappeared
This can be expected when OBJ does not support the texture, UV or material information stored by STL.
Fix: Keep the original STL visual dataThe model has missing faces
The STL source may contain open edges, invalid polygons, overlapping geometry or inverted normals that remain visible after conversion.
Fix: Inspect and repair the source geometryThe conversion fails on a large file
High polygon counts and complex geometry need more processing. Confirm the file is below 300 MB and opens correctly in a viewer.
Fix: Simplify unnecessary geometry detailSecure processing
Your 3D files remain yours
Product models can contain confidential engineering information. Privacy and file handling stay explicit beside the tool.
Encrypted upload
Files are transferred through a secure connection.
Automatic deletion
Uploaded and converted files are deleted after 7 days.
You retain ownership
Conversion does not transfer ownership of your model.
Not publicly listed
Your uploaded files are not added to the Marathon CAD library.
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Marathon OS Design Hub
Find a model before building from scratch
Browse engineering categories and recent 3D-printing models. Preview and validate every downloaded file before production use.
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Frequently asked questions
Everything to know before converting
Quick answers about formats, pricing, file limits, conversion quality and privacy.
How do I convert STL to OBJ online?
Upload your STL file (.stl) to Marathon OS, choose OBJ as the output format, and download the converted file in seconds — no software installation required.
Why convert STL to OBJ?
Converting STL to OBJ can help when you need a widely supported mesh format for rendering, game engines, or visualization tools.
What STL and OBJ file extensions are supported?
This converter accepts .stl input files and outputs .obj. Upload up to 300 MB per file.
Is the STL to OBJ converter free?
Files under 5 MB are free to convert and download on Marathon OS. Larger files may require a small fee per conversion.
How is my data stored and secured?
Your files are encrypted during upload, processed securely in the cloud, and automatically deleted after 7 days.
Do I need any special software or training?
No — upload your STL file and download OBJ directly in your browser. No plugins or desktop CAD tools required.
Can I convert large STL models to OBJ?
Yes — Marathon OS is optimized for large and complex CAD models. You can upload files up to 300 MB for STL to OBJ conversion.
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