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.

Is Marathon OS 3D File Converter free to use?

Files under 5 MB are free to convert and download. Larger files may require a small fee per conversion.

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.

Files under 5 MB free

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, 3DM, DWG and DXF files without installing desktop CAD software.

Free online converter | STEP, STL, IGES, OBJ, PLY, 3DM, DWG, DXF | Up to 300 MB | Auto-delete in 24 hours

Drag & drop your 3D file here to convert

or click to browse files

Files under 5 MB convert and download free. Larger files require a small fee per conversion — new file or re-run.

Supported formats: STEP (.step, .stp), IGES (.igs, .iges), STL (.stl), PLY (.ply), OFF (.off), BREP (.brp, .brep), OBJ (.obj), 3DM (.3dm), DWG (.dwg), DXF (.dxf)

Don't have a file? Try a sample:

Most Used CAD Conversion Tools

STEPSTL

For 3D printing and rapid prototyping

STEP3DM

For Rhino / OpenNURBS workflows

3DMSTEP

Move Rhino models into CAD/CAM

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

Browse CAD modelsExplore 3D models in various formats.Browse 2D technical drawingsFind and download technical drawings.Get CAD design supportConnect with experts for design assistance.

Supported CAD and 3D Formats

STEP
STL
IGES
OBJ
PLY
BREP
3DM
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/3DM): 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.

Need a proper native CAD file built from scratch?

Vetted designers deliver production-ready files in 24 hours — SolidWorks, Revit, Fusion 360 & more.

Hire a Designer

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.

Upload your CAD file

Drag & drop or browse to select your file

Choose the output format

STEP, IGES, STL, OBJ, PLY, OFF, BREP, or 3DM

Convert and download instantly

Download your converted file in one click

Upload CAD File Open CAD Viewer

Why use Marathon OS 3D CAD File Converter

Lightning-fast conversion

Convert in seconds with our cloud-based engine. No waiting.

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

STEPBREP

For solid geometry processing

STEPIGES

For cross-platform CAD exchange

STEPOBJ

For rendering and visualization

STEPPLY

For mesh and scan-style export

STEPSTL

For 3D printing and rapid prototyping

STEPOFF

For geometry research workflows

STEP3DM

For Rhino / OpenNURBS workflows

IGESBREP

For solid model processing

IGESSTEP

For modern CAD compatibility

IGESOBJ

For visualization pipelines

IGESPLY

For mesh export from legacy CAD

IGESSTL

For 3D printing from legacy files

IGESOFF

For geometry research workflows

IGES3DM

For Rhino / OpenNURBS workflows

OBJBREP

For solid CAD workflows

OBJIGES

For legacy CAD exchange

OBJSTEP

For CAD editing from mesh files

OBJPLY

For mesh interchange

OBJSTL

For mesh workflows and 3D printing

OBJOFF

For geometry research workflows

OBJ3DM

For Rhino mesh/NURBS handoff

PLYBREP

For solid CAD workflows

PLYIGES

For legacy CAD exchange

PLYOBJ

For rendering and editing

PLYSTEP

For CAD import from scan data

PLYSTL

For 3D printing pipelines

PLYOFF

For geometry research workflows

PLY3DM

For Rhino scan-data workflows

STLBREP

For solid reconstruction workflows

STLIGES

For legacy CAD exchange

STLOBJ

For game engines and 3D rendering

STLPLY

For mesh interchange

STLSTEP

For reverse engineering workflows

STLOFF

For geometry research workflows

STL3DM

For Rhino mesh workflows

OFFBREP

For solid CAD workflows

OFFIGES

For legacy CAD exchange

OFFOBJ

For visualization pipelines

OFFPLY

For mesh interchange

OFFSTL

For 3D printing pipelines

OFFSTEP

For modern CAD import

OFF3DM

For Rhino geometry workflows

BREPSTEP

For CAD/CAM handoff

BREPIGES

For legacy CAD exchange

BREPOBJ

For visualization pipelines

BREPPLY

For mesh export

BREPSTL

For additive manufacturing

BREPOFF

For geometry research workflows

BREP3DM

For Rhino / OpenNURBS workflows

3DMBREP

For solid CAD workflows

3DMIGES

For legacy CAD exchange

3DMOBJ

For visualization pipelines

3DMPLY

For mesh export

3DMSTL

For 3D printing pipelines

3DMOFF

For geometry research workflows

3DMSTEP

Move Rhino models into CAD/CAM

DWGDXF

Convert DWG to DXF for 2D CAD exchange

DXFDWG

Convert DXF to DWG for 2D CAD exchange

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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), 3DM (.3dm), DWG (.dwg), DXF (.dxf).
Is Marathon OS 3D File Converter free to use?
Files under 5 MB are free to convert and download. Larger files may require a small fee per conversion.
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.