How do I open a 3D file without installing software?

Drag the file onto a browser-based viewer. It renders in the page, so nothing is installed and nothing is sent to a desktop application. STEP, STL, IGES, OBJ, BREP, DXF, and GLB all open this way.

Which 3D file format am I looking at?

Read the extension. .stl, .obj, .glb and .gltf are mesh formats — the surface is triangles, which is what 3D printing and web graphics use. .step, .stp, .iges, .igs and .brep are solid CAD formats storing exact surfaces, which is what machining and CAD editing use. .dxf is a 2D drawing, not a 3D model.

Is there a file size limit?

Yes. Files up to 75 MB are accepted, and mesh formats must be under 25,000 triangles. Solid CAD formats such as STEP have no triangle limit because they store exact surfaces rather than facets.

Can I open a DWG or DXF drawing here?

DXF is accepted, but it is treated as a 2D profile that gets extruded into a solid — this is a 3D model viewer, not a 2D drafting viewer. DWG is not supported. For reading a 2D drawing as a drawing, use a DWG/DXF viewer instead.

Can I change the part after viewing it?

Yes. The model stays live — describe a change in plain English and it is applied to the geometry, then exported as STEP, STL, or 3MF. Viewing costs nothing; credits apply only when geometry is generated or changed.

Free Online 3D File Viewer

Someone sent you a 3D file and you just need to look at it. Drag it in below — STEP, STL, IGES, OBJ, BREP, DXF, or GLB — and it renders in your browser. Nothing to install, and viewing is free and uses no credits.

Drag your file onto the viewer above (or tap Upload). Don’t know what the extension means? The table below sorts it out. Want the full workspace? Open it in Studio.

What opens here

Format	Extensions	What it is	Dedicated page
STEP	.step · .stp	Exact CAD solid. No triangle limit	STEP viewer
STL	.stl	Triangle mesh — the 3D printing standard	STL viewer
GLB / glTF	.glb · .gltf	Web and AR mesh format	GLB viewer
OBJ	.obj	Mesh from scanning and sculpting tools	OBJ viewer
IGES	.iges · .igs	Older CAD exchange format, exact surfaces	IGES viewer
BREP	.brep · .brp	OpenCascade native solid format	—
DXF	.dxf	2D profile — extruded to a solid on import	What is a DXF

Not supported: DWG, SolidWorks (.sldprt), Inventor (.ipt), Parasolid (.x_t), 3MF import, and FBX. If your file is one of those, ask whoever sent it for a STEP export — every CAD package can produce one, and STEP is the format that survives the trip between programs intact.

Mesh or solid? It decides what you can do next

Every 3D file on that list falls into one of two families, and the difference matters the moment you want to do more than look:

Mesh — STL, OBJ, GLB

The surface is a shell of flat triangles. A cylinder is really a many-sided prism. Great for printing and for the web; poor for machining, because the curves are already approximations and no feature survived the export.

Solid — STEP, IGES, BREP

The file stores exact mathematical surfaces. A cylinder is a cylinder at any zoom. This is what a machine shop wants, and what edits like fillets and holes work reliably on.

Which one you have

Read the extension, or open it here and zoom into a curved edge. Visible facets mean a mesh. See STL vs STEP for the full comparison.

Converting between them

Solid to mesh is clean and lossless in the ways that matter — see STEP to STL. Mesh to solid is the hard direction and the facets do not become real curves again.

If a file will not open

Two limits account for nearly every failure, and both are worth knowing before you upload:

Limit	Applies to	What to do
75 MB file size	Every format	Export at lower resolution, or send the STEP instead of the mesh
25,000 triangles	Mesh formats only — STL, OBJ, GLB	Decimate in Blender, MeshLab, or your slicer, then retry

Scans, sculpted figures, and organic models routinely run to hundreds of thousands of triangles and will need decimating. Mechanical parts — brackets, gears, spacers, enclosures — almost never do. Solid CAD files have no triangle limit at all, which is one more reason to ask for the STEP.

When a browser viewer is the wrong tool

An honest comparison — this page is not always the right answer:

This viewer — fastest way to look at a file someone sent you, on any machine, with nothing installed. The only one of these that also lets you change the part afterwards.
Your slicer (Cura, PrusaSlicer, Bambu Studio, Orca) — the right choice when you are about to print, since it also gives you supports, orientation, and time estimates.
Windows 3D Viewer / macOS Preview — already installed and instant, for a mesh file you only need to glance at.
A DWG/DXF viewer — if what you actually have is a 2D drawing with dimensions on it, you want a drafting viewer, not a 3D one.
Blender or MeshLab — when the mesh needs repairing or decimating rather than viewing.

Change it, not just look at it

Where a plain viewer stops, the model here stays live — describe a change in plain English and PartWork.ai applies it to the geometry:

“add a 4 mm hole through the middle”
“make the base 3 mm thicker”
“export this as STEP”

Edits are more reliable on a solid than on a mesh, for the reason above: a mesh carries no feature history and its curves are already faceted. Uploading and viewing costs nothing; credits apply only when geometry is generated or changed.

Common questions

What program opens 3D files?

For a quick look, a browser viewer like this one. For printing, a slicer. For editing, CAD software — though which package can open your file depends entirely on the format, which is why STEP exists as the neutral exchange format.

How do I know what format to ask for?

Ask for STEP if the part is going to a machine shop or into CAD, and STL or 3MF if it is going to a 3D printer. See the right file format for a machine shop.

Is my file uploaded anywhere?

The file is uploaded to be converted and rendered — that is how the viewer opens formats a browser cannot read natively. See the privacy policy for what happens to it afterwards.

Does viewing cost anything?

No. Opening and inspecting a file is free and uses no credits. Credits are spent only when new geometry is generated or an existing part is changed.

Put this viewer on your own site

Selling prints, hosting a model library, or writing documentation? Embed this exact viewer on any page with one line — visitors inspect 3D files without leaving your site. Free and customizable.

<script src="https://cdn.partwork.ai/viewer/partwork_viewer_widget.js" defer></script>
<div data-partwork-viewer data-theme="dark" style="width:100%;height:520px"></div>

Colors, fonts, and viewer-only options are on the embed page.

Open your file

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