What a STEP file is

STEP (ISO 10303) is the standard format CAD programs use to exchange 3D models - SolidWorks, Inventor, Fusion, Creo and the rest all export it. Unlike an STL mesh it holds the exact shape, with true curves and usually its units, so it's what manufacturers, fabricators and suppliers send.

IGES (.igs or .iges) is an older exchange format that does the same job; the viewer opens it too.

Open it in your browser

  1. Open 3D Viewer in your browser.
  2. Drop the .step or .stp file on the page, or choose Open and pick it. A large assembly can take a few seconds to read.
  3. Turn, zoom and move the model with the mouse or your fingers.
  4. Use Measure for distances between points, and Section to cut through it. The model's size, volume and surface area show alongside it.

Make .step files open with a double-click

  1. Install Metre2 3D Viewer free from the Microsoft Store.
  2. Right-click a .step or .stp file and choose Open with > Choose another app.
  3. Pick Metre2 3D Viewer and select Always.

What a viewer can't do

  • It shows and measures the model; changing the design needs CAD software.
  • STEP files don't carry the original program's feature history, so even in CAD you get the shape, not the steps that made it.
  • Colours and part names come through when the file includes them.