Blog · How-to
How to view a STEP file without AutoCAD or Fusion 360
Someone sends you a .step or .stp file and you don't have AutoCAD, SolidWorks or a Fusion 360 license. You don't need any of them to look at the file. Here are the free options, ranked by how much you can actually do with the model afterwards.
Just want to look at it — browser viewer
If you only need to rotate the part and see what it is, a browser viewer is the fastest option. Open open3d.app/viewer in any modern browser and drop the .step file in. The viewer tessellates the geometry to a triangle mesh and displays it. No install, no account, file stays on your device.
Caveats: you cannot edit, measure precisely, or extract dimensions. It's a visual preview, not CAD.
FreeCAD — free desktop CAD with proper STEP support
FreeCAD is fully open-source parametric CAD that runs on Windows, Mac and Linux. It reads STEP natively via the OpenCascade kernel — the same kernel that paid tools use under the hood for CAD interchange. Quality of import is on par with Fusion or SolidWorks for most files.
- Download FreeCAD from freecad.org (free, no account).
- File → Open → pick the .step.
- You get the model as a solid body with editable features.
What you can do after import: measure between any two faces or edges, modify features (add holes, fillets, chamfers), export to STL or 3MF for printing, generate 2D drawings.
The UI takes some getting used to — FreeCAD's workbenches are organised by domain (Part, PartDesign, Draft, TechDraw) which is different from Fusion's single-window approach. There are good free tutorials on YouTube.
eDrawings (Windows, Mac) — free official viewer
Dassault, the company behind SolidWorks, publishes eDrawings as a free viewer. It reads STEP, IGES, SolidWorks files and others. Quality is excellent, the install is heavyweight but trouble-free.
Good for: measurement, section views, exploded views if the STEP includes assembly structure.
Not so good for: editing (it's a viewer only).
Cad Assistant — free, lightweight, cross-platform
Open Cascade publishes Cad Assistant — a free viewer that reads STEP, IGES, BREP, OBJ and several others. Runs on Windows, Mac, Linux and even Android/iOS. Lighter than eDrawings and quicker to install.
Has measurement tools, exports to STL for printing, supports assembly trees. A good middle ground if FreeCAD feels too heavy and the browser viewer feels too limited.
Online Onshape — full cloud CAD, free for personal projects
Onshape is browser-based parametric CAD with full STEP import. Free tier lets you store unlimited public documents. If your project is okay being public, Onshape gives you near-Fusion-level capability without installing anything.
Limits: free tier makes everything public, so don't use it for confidential client work.
What you cannot do with viewer-only tools
Browser viewers and basic viewers like Cad Assistant cannot:
- Modify the model's features (extrude, fillet, chamfer).
- Generate machining toolpaths for CNC.
- Run finite element analysis.
- Combine multiple STEPs into an assembly.
For any of those, you need real CAD — FreeCAD covers most of them for free.
What about mobile?
iPhone and Android can both view STEP through browser viewers — open the file in mobile Safari or Chrome and use a web-based viewer. There are also a few native STEP viewer apps on each app store; check reviews carefully because some are wrappers around free engines with paid-tier annoyances.