Instant preview
Quickly open and inspect CAD files without installing heavy software.
Free online tool
BREP File Viewer – Instantly Open & Explore BREP Files
Effortlessly view and inspect BREP (.step, .stp, .stl, .ply, .off, .igs, .iges, .brp, .brep, .obj) files online. Marathon OS CAD Viewer delivers fast, secure, and high-performance rendering with no downloads needed.
Private uploads
Auto-delete in 24hrs
Up to 300 MB
Drag & drop your 3D files here
or click to browse files
Supported formats:
Don't have a file? Try a sample:
HOW IT WORKS
How to view 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
Preview in browser
View, zoom, pan and inspect your 3D model
03
Share or convert
Download or convert to another format
Why use Marathon OS CAD Viewer
Format support
Common exchange formats supported — STEP, IGES, STL, OBJ, PLY, BREP & more.
Faster collaboration
Share files with teammates for quick review — no plugins needed.
Anywhere access
Review models from any device — desktop, tablet, or mobile.
View popular CAD formats
Supported format viewers
OBJViewer
View OBJ mesh models and 3D assets in your browser.
STLViewer
Inspect STL meshes for 3D printing checks.
PLYViewer
Open PLY point clouds and polygon meshes online.
OFFViewer
Preview OFF geometry files without desktop software.
IGESViewer
Preview IGES/IGS surfaces before manufacturing handoff.
BREPViewer
Open BREP boundary representation models in the browser.
STEPViewer
Open STEP/STP assemblies and 3D geometry online.
STPViewer
View STP (STEP) CAD files instantly—no install needed.
BRPViewer
Inspect BRP (BREP) solid models for design review.
IGSViewer
Check IGS/IGES exchange files for collaboration.
Marathon-OS Design Hub
Everything you need to design faster, smarter, and with more impact.
and whether you see any voice-only plans under
Refactor this into a single reusable resolver Or write a safe CREATE + UPDATE version
I’ll tell you exactly where the unaccepted file is coming from.
Use this if you want a clean linear history (best for teams).
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USE CASES
Who this CAD viewer is for
Mechanical engineers reviewing STEP/IGES from vendors
✓ reviewing STEP/IGES from vendors
Manufacturing teams checking files before quoting
✓ checking files before quoting
Design teams quickly sharing 3D previews internally
✓ quickly sharing 3D previews internally
Students opening CAD files without expensive software
✓ opening CAD files without expensive software
3D printing workflows inspecting STL/OBJ meshes
✓ inspecting STL/OBJ meshes
Privacy and file handling
Private uploads
Files are processed securely.
Retention
Files are deleted after 24 hours immediately.
Ownership
You retain full ownership of your files.
Need to convert a CAD file?
Sometimes you need a different format for manufacturing, printing, or sharing. Use our 3D File Converter to convert between STEP, IGES, STL, OBJ and more.
Convert 3D Files →Empowering Industries Across the Product Lifecycle
From automotive to aerospace, Marathon OS helps engineering and manufacturing teams collaborate faster, manage complex designs, and drive innovation — all in one place.
Marine & Shipbuilding
Marine engineering involves massive structural components and multi-disciplinary designs. Marathon OS ensures every stakeholder accesses the latest CAD and documentation versions.
Architecture & Construction
Architectural and construction firms deal with large blueprints and 3D models. Marathon OS enables online access, commenting, and streamlined sharing of all formats.
PCB & Electrical Engineering
Electrical engineers manage PCBs, schematics, and layouts with high detail. Marathon OS keeps design files versioned, accessible, and linked to your product lifecycle.
Scientific Research & Simulation
Research projects use simulation models, test data, and analysis files. Marathon OS helps store, view, and collaborate on these assets while preserving data integrity.
Jewelry & Watchmaking
This industry demands precision in micro-scale designs. Marathon OS makes it easy to preview, iterate, and organize detailed CAD files for intricate creations.
3D Printing & Prototyping
Rapid prototyping demands quick file access and iteration. Marathon OS supports file conversion, model previews, and team collaboration for 3D printing workflows.
Medical & Healthcare
From surgical instruments to wearables, medical devices need compliant design systems. Marathon OS helps manage revisions, approvals, and secure file sharing with teams.
Aerospace & Aviation
Aerospace requires ultra-precise engineering with strict compliance standards. Marathon OS offers secure design sharing, multi-team access, and lifecycle traceability for every part.
Automotive Industry
The automotive sector designs complex mechanical systems, from engines to interiors. Marathon OS streamlines part management, CAD collaboration, and version control across engineering teams.
Video Games & Virtual Reality
Game and VR developers work with 3D assets and environments. Marathon OS enables cross-team collaboration on models, textures, and design feedback — online.
Manufacturing & CNC
Manufacturing relies on precision and process integration, especially with CNC machining. Marathon OS centralizes design files, toolpaths, and revision data in one place.
Robotics & Automation
Robotics blends mechanics, electronics, and software — requiring synchronized development. Marathon OS enables shared CAD views, modular design tracking, and change management.
Frequently asked questions
Find answers to common questions about Marathon OS CAD Viewer.
What is a CAD viewer?
A CAD viewer lets you open and preview 2D/3D CAD files without editing them—useful for quick reviews and sharing.
Can I open STEP and IGES files online?
Yes—upload your .step/.stp or .igs/.iges file to preview it directly in your browser.
Do I need to install any software?
No. Marathon OS CAD Viewer is browser-based—no downloads required.
Which file formats are supported?
STEP/STP, IGES/IGS, STL, OBJ, PLY, OFF, BREP.
Is this CAD viewer free?
Yes—this page is presented as a Free Online CAD Viewer, with usage constraints like an upload size limit (up to 300 MB per file).
What is the max file size?
Up to 300 MB per upload.
Will my file stay private?
Files stay private, are encrypted, and are automatically deleted after 24 hours; see the Privacy Policy for details.
Why does my model look broken (holes/missing faces)?
Some CAD exchange formats (especially surface-based files like IGES) may import with gaps. Try converting to STEP or re-exporting with healed/stitched surfaces.
Can I convert my file to another format?
Yes—use the 3D File Converter at /tools/3d-cad-file-converter.
Does it work on Mac / Windows?
Yes—because it runs in your browser (no installation needed), it works on Mac and Windows with a modern browser.
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