How to open a STEP file online
- Drop the .step / .stp file into the box above or click Choose file.
- Drag to rotate, scroll or pinch to zoom, right-drag or two-finger drag to pan.
- Use the buttons for front / top / side views, wireframe and screenshots.
- Pick an output format on the right to convert and download.
What the viewer shows
- Dimensions of the bounding box (X × Y × Z) in millimetres.
- Triangle count and number of parts.
- Surface area and volume (for closed meshes).
- Watertight check – whether the mesh is closed, which matters for 3D printing.
About STEP files
STEP (ISO 10303 (STEP AP203/AP214/AP242)) was standardised as ISO 10303 for exchanging engineering data between CAD systems. It describes exact solid geometry (B-rep surfaces, edges and assemblies) rather than triangles. It is the neutral CAD format used by SolidWorks, Fusion 360, Inventor, CATIA, FreeCAD and Onshape.
Desktop programs that open STEP
- FreeCAD (free)
- Fusion
- SolidWorks and eDrawings
- Onshape
- Inventor, CATIA, Creo, NX
Frequently asked questions
Is the viewer free?
Yes – viewing is free and unlimited, without an account. Converting and downloading is free for up to 3 files a day; Pro removes the limit.
Is my file uploaded?
No. The file is read by your browser and rendered with WebGL on your device. It is never sent to a server.
Do I need CAD software to open a STEP file?
No. This viewer uses the OpenCascade geometry kernel compiled to WebAssembly, the same kernel FreeCAD uses, to read the file directly in your browser.
Can it open assemblies?
Yes. All bodies in the file are loaded with their colours; part names are kept where the file provides them.
Does it work on iPhone and Android?
Yes. Open the page in Safari or Chrome, tap Choose file and pick the model from Files or Downloads.