STEP vs STP: What's the Difference and How to Open Them Without CAD Software

Are STEP and STP the same format? How do you open them without SolidWorks, CATIA, or Fusion 360? Clear answers and practical solutions.

STEP and STP: two extensions, one format

There is no technical difference between a .STEP file and a .STP file. They are two file extensions for the same format: ISO 10303, the international standard for CAD data exchange. The .STEP extension is more common, but some software like SolidWorks defaults to .STP on export. The file content is identical.

Why do two extensions exist?

The .STP extension comes from legacy DOS systems that limited file extensions to 3 characters. The .STEP extension became common with modern systems that accept longer extensions. Both are recognized by all modern CAD applications.

What software can open STEP and STP files?

• SolidWorks — native STEP/STP support
• Fusion 360 — native STEP/STP support
• CATIA — native STEP/STP support
• FreeCAD — free, open-source, supports STEP/STP
• eDrawings — lightweight SolidWorks viewer, requires installation
• OmniView 3D — browser-based, no installation required

How to open a STEP file without installing CAD software

If you don't have SolidWorks or Fusion 360, the fastest solution is to upload your STEP file to OmniView 3D. The file converts to an interactive 3D viewer in under 60 seconds. You can rotate the model, zoom, and activate exploded view — directly in your browser, on desktop or mobile.

Does a STEP file contain colors and materials?

It depends on the STEP profile used during export. The AP214 profile includes surface colors. The older AP203 profile does not. The exact geometry (shape, dimensions, tolerances) is always present in both profiles. PBR textures and render materials are not part of the STEP format — those are specific to web formats like GLB.