Free Online STEP File Viewer
Open a .step or .stp file and inspect the 3D model right in your browser — rotate it, zoom in, check dimensions. Nothing to install, and viewing a file is free and uses no credits. IGES, BREP, DXF, OBJ, and STL open the same way.
Open your file: Launch the viewer — then use the upload button and pick your file. It renders in the 3D view, and you can keep it there to make changes afterwards.
What you can open
| Format | Extensions | Typically comes from |
|---|---|---|
| STEP | .step · .stp | The universal CAD exchange format — every major package exports it |
| IGES | .iges · .igs | Older exchange format, still common from legacy systems |
| BREP | .brep · .brp | OpenCascade native boundary representation |
| DXF | .dxf | 2D profiles — laser, plasma, waterjet. Needs an extrusion height to become 3D |
| OBJ | .obj | Triangle mesh, often from 3D scanning or sculpting |
| STL | .stl | 3D printing mesh — see the STL viewer |
Size limit 75 MB. Mesh formats (OBJ, STL) additionally cap at 50,000 triangles, because converting a mesh into solid geometry is memory-hungry. STEP and IGES have no triangle limit — they describe exact surfaces rather than triangles, which is one reason STEP is the better format to ask for when you have the choice.
What a STEP file actually is
A STEP file (ISO 10303) is the neutral exchange format of the CAD world. It stores exact geometry — real curved surfaces described mathematically, not an approximation made of triangles. That is why a machine shop asks for STEP: the curve you designed is the curve they cut.
.step vs .stp
Identical. The three-letter form is a leftover from when Windows required short extensions. Both open the same way.
Exact, not triangulated
A cylinder in STEP is a cylinder. In STL it is a few hundred flat facets pretending to be one.
Editable downstream
Because the surfaces are real, features like holes and fillets can still be added cleanly after import.
Universally supported
SolidWorks, Fusion 360, Onshape, FreeCAD, Inventor, and CATIA all read and write it.
Opening a STEP file without CAD software
You do not need a CAD licence to look at a part someone sent you. Three routes, depending on what you need next:
- Just look at it — open it here in the browser. Fastest option, nothing to install, no cost.
- Look at it and change something — open it here, then describe the change in plain English and export the result.
- Full parametric editing with feature history — you want real CAD software. FreeCAD is free and open source; Fusion 360 and Onshape have free tiers for personal use. Honest answer: for deep modelling work, use the real thing.
Viewing is where most tools stop
Every free STEP viewer will render your part. The question is what happens next. With PartWork.ai the model stays live after import, so you can ask for a change in plain English instead of re-modelling it somewhere else:
“add a 5 mm hole through the centre”
“fillet the top edges 2 mm”
“make the base 10 mm thicker”
“export this as STL for printing”
Then export as STEP for machining, or STL / 3MF for printing. Uploading and viewing costs nothing; credits are only used when you ask for geometry to be generated or changed.
Common questions
How do I open a STEP file without SolidWorks or AutoCAD?
Upload it to a browser-based viewer like this one. STEP is a neutral standard, so no specific CAD package is required to display it.
Is .stp the same as .step?
Yes, byte-for-byte the same format. Only the extension differs, for historical Windows reasons.
Does viewing cost anything?
No. Opening and inspecting a file uses no credits. Credits apply only to generating or modifying geometry.
Why will my file not open?
Most often it is over the 75 MB limit, or it is a format we do not read — notably DWG and native files like .sldprt or .f3d. Re-export as STEP from whatever created it and it will open. An assembly saved with no solid bodies (datums or reference geometry only) will also come through empty.
What if I need to measure it?
Dimensions of the overall part are shown on import. For feature-level measurement, export to a full CAD package — see measuring a part for replacement.
Open your file
Launch the viewer, upload your .step or .stp file, and it renders in the 3D view. Free, in the browser, nothing to install.