# STEP File Viewer

> Open STEP and STP files from SolidWorks, Fusion, Onshape or FreeCAD in your browser. Assemblies, part colors and real dimensions, with no CAD seat and no upload.

Page: https://printpal.io/tools/step-viewer
Updated: 2026-11-12
Use it: open https://printpal.io/tools/step-viewer in a browser and drop a file. Free, no account, files are processed locally and never uploaded.

STEP (ISO 10303) is how CAD programs hand each other exact geometry: cylinders, fillets and splines stored as math and grouped into parts and assemblies. A browser can't draw math directly, so the viewer runs **OpenCascade**, the open-source geometry kernel behind FreeCAD, compiled to WebAssembly, and turns every face into triangles on your device.

The first STEP you open downloads the reader once (about 7 MB); after that your browser caches it. Each part keeps its color from the file (AP214 and AP242 carry colors, AP203 does not), dimensions are shown in millimetres whatever unit the file was saved in, and you can save the result as STL or 3MF for printing.

## How to use the STEP viewer

1. **Open the file.** Drop .step or .stp files. The STEP reader (about 7 MB) downloads the first time.
2. **Check size and orientation.** The model stands on the plate in millimetres. Switch to inches, or change the file units or up axis if it looks wrong.
3. **Run the checks.** Read the mesh check, pick your printer to see whether it fits, and use Measure (M) or Section (X) for a closer look.
4. **Save or convert.** Take a PNG screenshot, or save the model as STL, 3MF, OBJ, GLB, PLY or USDZ.

## What you can check

- Assemblies with every part in place, colored as in AP214 and AP242 files
- Overall size in mm or inches, plus volume and surface area of closed solids
- Point-to-point measurements on the meshed surface
- Section view to look inside housings and assemblies
- Save as STL, 3MF, OBJ or GLB at Draft, Normal or Fine quality

## STEP at a glance (ISO 10303-21 (Standard for the Exchange of Product model data))

STEP is the ISO standard for exchanging exact CAD geometry. Unlike a mesh it keeps true curves, so a 10 mm hole stays a perfect 10 mm cylinder until something turns it into triangles.

- **Stores:** Exact B-rep solids: planes, cylinders, fillets and splines as math, in assemblies
- **Color:** Per part and per face in AP214 and AP242; none in AP203
- **Units:** Declared in the file, usually millimetres
- **Up axis:** Whatever the CAD used; usually Z
- **Meshing:** Needs tessellation into triangles before printing or rendering
- **Opens in:** SolidWorks, Fusion, Onshape, FreeCAD, Inventor, CATIA, NX; Bambu Studio, OrcaSlicer, PrusaSlicer

## Tips

- **Slow first open?** Large assemblies with hundreds of parts take a while to mesh. Switch the CAD quality to Draft for a quick first look.
- **How exact are the measurements?** Points land on triangles, so a measurement across a curved face can be off by the chord error, about 0.05% of the part's size at Normal quality. Use your CAD tool for tolerance work.
- **Printing it?** Save as STL or 3MF from the sidebar, or use [STEP to STL](https://printpal.io/convert/step-to-stl) for batches and quality options. Bambu Studio, OrcaSlicer and PrusaSlicer can also import STEP directly.

## FAQ

### What is the difference between STEP and STP?

None. .step and .stp are two extensions for the same ISO 10303-21 file, and the viewer opens both.

### Can I view a STEP file without CAD software?

Yes. This page reads STEP in your browser on any modern computer, tablet or phone. You can rotate, measure and section it, but not edit features; that takes CAD such as FreeCAD, Fusion or Onshape.

### Does it open IGES files too?

Yes. [IGES files](https://printpal.io/tools/iges-viewer) (.iges, .igs) use the same OpenCascade reader.

### Is my CAD file uploaded?

No. The reader runs in your browser; only the reader program is downloaded, from a public CDN. Your design stays on your device.

### Is the viewer free? Are there limits?

Free, with no sign-up, watermark or file limit. The practical limit is your device's memory: files of a few hundred MB open on most laptops.

### Are my files uploaded anywhere?

No. Files are read by JavaScript and WebAssembly in your browser and never sent to PrintPal. Only the code is downloaded, and the STEP and IGES reader once, from a public CDN.

## Related

- [STEP to STL Converter](https://printpal.io/convert/step-to-stl)
- [STEP to OBJ Converter](https://printpal.io/convert/step-to-obj)
- [STEP to 3MF Converter](https://printpal.io/convert/step-to-3mf)
- [STL to OBJ Converter](https://printpal.io/convert/stl-to-obj)
- [OBJ to STL Converter](https://printpal.io/convert/obj-to-stl)
- [STL to 3MF Converter](https://printpal.io/convert/stl-to-3mf)
- [GLB to STL Converter](https://printpal.io/convert/glb-to-stl)
- [STL Viewer](https://printpal.io/tools/stl-viewer)
- [3D model viewer](https://printpal.io/tools/3d-model-viewer)
- [3D model converter](https://printpal.io/tools/3d-model-converter)
- [Mesh Repair](https://printpal.io/tools/mesh-repair)
- PrintPal for LLMs: https://printpal.io/llms.txt