Lightning-fast conversion
Convert in seconds with our cloud-based engine. No waiting.
Free online tool
Free Online 3D CAD File Converter
Convert CAD and 3D files between common engineering formats in your browser. Upload securely and convert STEP, STL, IGES, OBJ, PLY, BREP, DWG and DXF files without installing desktop CAD software.
Free online converter | STEP, STL, IGES, OBJ, PLY, DWG, DXF | Up to 300 MB | Auto-delete in 24 hours
Drag & drop your 3D files here to convert
or click to browse files
Supported formats: STEP (.step, .stp), IGES (.igs, .iges), STL (.stl), PLY (.ply), OFF (.off), BREP (.brp, .brep), OBJ (.obj), DWG (.dwg), DXF (.dxf)
Don't have a file? Try a sample:
Most Used CAD Conversion Tools
STEPSTL
For 3D printing and rapid prototyping
STLSTEP
For reverse engineering workflows
DXFDWG
Convert DXF to DWG for 2D CAD exchange.
DWGDXF
Convert DWG to DXF for 2D CAD exchange.
STEPIGES
For cross-platform CAD exchange
IGESSTEP
For modern CAD compatibility
OBJSTL
Convert OBJ to STL for mesh workflows and 3D printing.
STLOBJ
For game engines and 3D rendering
Need to preview before converting?
Open your CAD file in the Marathon OS 3D viewer first to inspect geometry, check scale and confirm the model before converting it to another format.
Open CAD Viewer →Explore Marathon OS CAD resources
Supported CAD and 3D Formats
- STEP
- STL
- IGES
- OBJ
- PLY
- BREP
- DWG
- DXF
When to use the CAD file converter
Use the CAD file converter when you need to prepare files for 3D printing, CAD review, supplier handoff, manufacturing, prototyping or design collaboration.
Conversion quality notes (read before converting)
- CAD → Mesh (STEP/IGES/BREP → STL/OBJ/PLY): may lose parametric features; output becomes triangles.
- Mesh → CAD (STL/OBJ/PLY → STEP/IGES/BREP): may produce surfaces/approximations depending on engine.
- If output looks broken, try converting to STEP first, then to your target format.
Explore more
Need to preview before converting?
Open CAD Viewer →Looking for ready-to-use CAD files?
Browse CAD Library →HOW IT WORKS
How to convert CAD files online
No downloads. No plugins. Works right from your browser.
01
Upload your CAD file
Drag & drop or browse to select your file
02
Choose the output format
STEP, IGES, STL, OBJ, PLY, OFF, or BREP
03
Convert and download instantly
Download your converted file in one click
Why use Marathon OS 3D CAD File Converter
No installation required
Works in your browser — no downloads or plugins needed.
Handles large & complex models
Optimized for large and intricate CAD files up to 300 MB.
Secure & private
Encrypted uploads. Files automatically deleted after 24 hours.
Your files, your IP
Full file ownership stays with you. We never share your data.
Available 24/7
Convert files anytime, anywhere — no restrictions.
Privacy and file handling
Encrypted uploads + secure processing
Files are encrypted during upload and processed securely.
Automatic deletion after 24 hours
Uploads are automatically deleted after 24 hours.
File ownership stays with you
You retain full ownership of your files.
Popular conversions.
CAD Converter Types
STEPSTL
For 3D printing and rapid prototyping
STEPIGES
For cross-platform CAD exchange
STEPOBJ
For rendering and visualization
IGESSTEP
For modern CAD compatibility
IGESSTL
For 3D printing from legacy files
STLSTEP
For reverse engineering workflows
OBJSTEP
For CAD editing from mesh files
BREPSTL
For additive manufacturing
STLOBJ
For game engines and 3D rendering
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Frequently asked questions
Find answers to common questions about Marathon OS 3D CAD File Converter.
What is Marathon OS 3D CAD File Converter?
Marathon OS 3D File Converter is a browser-based tool that lets you convert CAD/3D file formats online—no software installation needed.
What file formats are supported?
STEP (.step, .stp), IGES (.igs, .iges), STL (.stl), PLY (.ply), OFF (.off), BREP (.brp, .brep), OBJ (.obj), DWG (.dwg), DXF (.dxf).
Is Marathon OS 3D File Converter free to use?
Yes! It’s completely free with no usage limits or hidden costs. Just drag, drop, and convert.
How is my data stored and secured?
Your files are encrypted during upload, processed securely, and automatically deleted after 24 hours.
Do I need any special software or training?
No—just upload your file and convert it directly in your browser (no downloads/plugins).
Can I convert large and complex CAD models?
Yes—the page states it's optimized to handle large & complex models, and supports uploads up to 300 MB.
What is the max file size?
You can upload files up to 300 MB.
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