STEP is the industry-standard exchange format for parametric CAD data. It stores exact boundary-representation (B-rep) geometry — true curves and surfaces rather than triangles — which makes it the preferred way to move solid models between CAD systems like SolidWorks, Fusion 360, Inventor, CATIA and NX without losing precision.
SolidWorks, Fusion 360, Inventor, Creo, CATIA and NX all export STEP, and it is what suppliers, machine shops and part libraries send when they cannot send a native CAD file. ISO 10303 is vendor-neutral, which is exactly why it arrives in your inbox.
Best for: Exchanging precise mechanical parts and assemblies between CAD systems. There is a fuller write-up on the STEP format reference page.
Every format on this site also gets the same viewport tools: orbit, pan and zoom with fit-to-view, isometric and the six standard views, a perspective/orthographic toggle, shaded, shaded-with-edges, wireframe and X-ray display, hide-selected, and a PNG screenshot of the current view. The same controls are on the general 3D and CAD viewer, which accepts every importable format at once.
Worth knowing before you rely on it. A viewer that overstates what it can read wastes more of your time than one that is specific about its limits.
| STEP files | |
|---|---|
| Extensions | .step, .stp |
| Geometry | Exact B-rep solids & surfaces |
| Units | Yes, embedded |
| Colors & materials | Per-part colors |
| Animations | No |
| Typical use | CAD exchange between engineering tools |
STEP embeds its units and the kernel is asked for millimetres, so the dimensions, area and volume readouts are true millimetre values rather than bare numbers.
STEP is a source format here — it can be read but not written, because a tessellated solid written back into STEP is a file no CAD kernel wants. The converter runs on the same local pipeline as this viewer, so a conversion is just as private as a preview: STEP to STL is the usual choice.
Yes. This page renders .step and .stp files with a full CAD geometry kernel compiled to WebAssembly, so you get the assembly tree, section views and measurements without installing SolidWorks, Fusion 360 or Inventor, and without an account.
No. The file is read from disk by the page itself and parsed by the CAD kernel inside your browser tab. There is no server-side conversion step, which is why confidential parts are safe to open here.
Because STEP surfaces have to be tessellated before a GPU can draw them. The viewer uses a fine setting (0.1% of the bounding box), but a facet count is still a facet count — zoom far enough into a fillet and you will see the triangles.
No, and no STEP viewer can. A STEP file holds geometry, assembly structure, part names and colors. Features, sketches and parameters are never written into it, so there is nothing to display.
Geometry: exact b-rep solids & surfaces. Units: yes, embedded. Colors and materials: per-part colors. Animations: no. Of that, the viewer draws geometry and flat base colors; texture maps and animation are never displayed. STEP embeds its units and the kernel is asked for millimetres, so the dimensions, area and volume readouts are true millimetre values rather than bare numbers.
Read the STEP format reference for the format itself, open the general 3D and CAD viewer if you have several formats to look at, or start from the 3D and CAD converter.
If the model is heavier than it needs to be, the mesh simplifier reads .step directly, tessellating the CAD geometry first, decimates it in your browser and previews the result before you export. If the file is headed for a 3D printer, the G-code viewer shows the sliced toolpath layer by layer once your slicer has run.
You received a .step or .stp file but have no CAD program installed. Here are your options — including a free browser-based STEP viewer that needs no install.
STEP stores exact CAD geometry, STL stores triangles. Understand the difference, when each format wins, and how to convert between them for free.
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