How do I open a STEP file for free?

FreeCAD opens and edits STEP files on Windows, macOS and Linux at no cost. To simply look at a model on Windows, the built-in 3D Viewer displays it without installing anything.

Are .step and .stp the same?

Yes, identical. Both are ISO 10303 files and the shorter spelling is a leftover from three-character extension limits. Any tool reading one reads the other.

What is the difference between STEP and STL?

STEP holds exact solid geometry you can edit and measure. STL holds a triangle mesh of the surface, which is what 3D printers need but which cannot be meaningfully edited as CAD.

File extensions

How to open a .step file

STEP 3D model · CAD / 3D

A .step file is a 3D CAD model in an open standard format. FreeCAD opens and edits it for free, and on Windows 10 or 11 the built-in 3D Viewer displays one on a double-click.

What a .step file actually is

STEP is ISO 10303, the neutral exchange format for 3D CAD. It stores true solid geometry, so surfaces stay mathematically exact rather than being approximated by triangles.

That is the key difference from STL. A STEP model can be edited, dimensioned and machined from; an STL is a mesh shell suitable for printing and little else.

The same format also uses the .stp extension. They are identical, and the two spellings survive from the old three-character limit.

Why it will not open

macOS has no native support, and on Windows the built-in 3D Viewer handles STEP but is not associated with the extension by default, so a double-click asks which program to use.

Step by step

Windows

01To view quickly: right-click, choose "Open with", then 3D Viewer, which ships with Windows 10 and 11.
02To edit or measure: install FreeCAD, which is free and open source and imports STEP with the solid geometry intact.
03To convert for 3D printing, open it in FreeCAD and export as STL, choosing the mesh resolution during export.

macOS

01macOS has no built-in STEP viewer.
02Install FreeCAD, or "brew install --cask freecad", which opens and edits the format.

What usually goes wrong

Do not convert to STL unless you must

Exporting STEP to STL throws away the exact geometry and replaces it with triangles. That is fine for printing and terrible for further engineering work. Always keep the STEP as the master file.

Why there is no download list here

We index 177 programs and none of them opens .step files, so there is nothing for us to publish a verified download for. The software named in the steps above is the right answer for this format; we simply do not have its installer on record yet.

Common questions

How do I open a STEP file for free?: FreeCAD opens and edits STEP files on Windows, macOS and Linux at no cost. To simply look at a model on Windows, the built-in 3D Viewer displays it without installing anything.
Are .step and .stp the same?: Yes, identical. Both are ISO 10303 files and the shorter spelling is a leftover from three-character extension limits. Any tool reading one reads the other.
What is the difference between STEP and STL?: STEP holds exact solid geometry you can edit and measure. STL holds a triangle mesh of the surface, which is what 3D printers need but which cannot be meaningfully edited as CAD.