Instant preview
Quickly open and inspect CAD files without installing heavy software.
Free online tool
Free Online DWG File Viewer
Open and inspect DWG files online without installing CAD software. Marathon OS lets you preview DWG CAD drawings securely in your browser with private uploads and automatic file deletion after 24 hours.
Free online viewer | Private uploads | Up to 300 MB | Auto-delete in 24 hours | No CAD software needed
Drag & drop your 3D files here
or click to browse files
Supported input formats: DWG (.dwg)
Don't have a file? Try a sample:
What is a DWG file viewer?
A DWG file viewer lets you open and inspect DWG files online without installing desktop CAD or 3D software.
When to use this viewer
Use this viewer when you need to inspect a model, check geometry, review a file from a supplier, preview a downloaded CAD file or confirm the file before conversion.
What to check before using the file
Check model scale, missing faces, broken geometry, assembly structure and whether the file is suitable for conversion, 3D printing, design review or manufacturing handoff.
Need to convert a CAD file?
If you need the file in another format, use Marathon OS CAD Converter to convert between STEP, STL, IGES, OBJ, PLY, BREP, DWG and DXF.
Convert 3D CAD Files →Explore Marathon OS CAD resources
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.
Marathon-OS Design Hub
Everything you need to design faster, smarter, and with more impact.
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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.
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.
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.
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.
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.
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.
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.
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.
Marine & Shipbuilding
Marine engineering involves massive structural components and multi-disciplinary designs. Marathon OS ensures every stakeholder accesses the latest CAD and documentation versions.
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.
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.
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.
Explore more industries
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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