STL vs STEP vs 3MF: Which File Should You Upload?

Last updated October 2026

Short answer: upload a 3MF if you have one, a STEP if you designed it in CAD, and an STL for everything else. Rapid3D.ie accepts all of them, plus OBJ.

STL

The most common 3D printing file. Almost every model you download is an STL. It doesn’t store units or colours, so check the size on the quote tool before you order.
Best for: single-colour prints and downloaded models.

3MF

The modern version of STL. It stores the size, the colours and several parts in one file.
Best for: multi-colour prints and projects with several parts.

STEP (.stp)

A file from CAD software like Fusion, Onshape or SolidWorks. It’s the most accurate format, so curves stay smooth and holes stay the right size.
Best for: engineering parts that need to fit something.

OBJ

Common from 3D scanning and Blender. We print OBJ files in one colour.
Best for: sculpts and scans.

Exporting from CAD?

Set the STL export quality to high or fine. On a low setting, curves come out with flat edges.

Still not sure? Upload whatever you have to our quote tool and we’ll check it before printing.