Free tool

Free Online STEP File Viewer

Open a STEP or STP file to rotate, zoom, and check its size. No account, no install. IGES, STL, and DXF files open here too.

Your file stays on your computer. Nothing is uploaded.

How OpenSpindle works

We tap our partner network. You get the best-match quote.

Upload your part and we tap our network of partner shops to get you a competitive, all-in quote that is the best match for the job.

One upload

A CAD file or a sketch. That is the whole ask on your end.

Your best-match quote

Sourced from the partner shops set up for your exact part.

All-in, on your timeline

Machining, finishing, and shipping detailed to your turnaround.

STEP is the standard neutral format for 3D CAD parts and assemblies. Drop a .step or .stp file above and it opens in your browser, where you can orbit, zoom, switch to wireframe, and see the part's overall dimensions. The file is parsed on your computer and is not uploaded anywhere unless you choose to request a quote.

What is a STEP file?

STEP stands for Standard for the Exchange of Product model data, defined by ISO 10303. A STEP file stores exact solid geometry as a boundary representation: faces, edges, and true curved surfaces such as cylinders, cones, and splines, rather than an approximation made of triangles. It can also store assembly structure, so one file can hold many parts and how they fit together.

Because STEP is neutral, most CAD programs can read and write it, including SolidWorks, Fusion, Inventor, Creo, NX, Onshape, and FreeCAD. That is why machine shops ask for STEP files: the geometry opens in their CAM software with exact dimensions, whatever program you designed in. The .step and .stp extensions are the same format.

How to open a STEP file

  • In your browser: drop the file into the viewer above. Nothing to install, and the file stays on your computer.
  • Free desktop software: FreeCAD (free and open source) opens and edits STEP files on Windows, Mac, and Linux.
  • Your CAD program: use File > Open or Import in SolidWorks, Fusion, Inventor, Onshape, or similar. Most bring the part in as an editable solid body without its original feature history.

If you only need to check a part before sending it out, a viewer is enough. If you need to change it, import it into CAD.

STEP vs IGES vs STL

All three move 3D geometry between programs, but they store different things. For machined, sheet metal, or molded parts, send STEP.

FormatGeometryUnitsAssembliesBest for
STEP (.step, .stp)Exact solids and surfacesStored in the fileYesMachining, sheet metal, molding
IGES (.iges, .igs)Exact surfaces, often without a closed solidStored in the fileLimitedOlder CAD and CAM systems
STL (.stl)Triangle mesh approximationNot storedNo3D printing

A direct STL-to-STEP conversion keeps the flat triangles; it does not recover true curved surfaces.

What a STEP file does not tell a shop

A STEP file carries shape, not requirements. Most STEP exports do not include tolerances, thread callouts, surface finish, material, or heat treatment. The AP242 version of STEP can carry this product manufacturing information, but most exports leave it out.

For anything that matters, such as tapped holes, tight tolerances, or a cosmetic finish, send a PDF drawing with the STEP file. See the thread callout guide and how to prepare CAD files for a quote.

Why a STEP file might not display

Most display failures come from exports that contain loose surfaces instead of a closed solid, or from unusual geometry the exporter wrote in a nonstandard way. Try exporting again as a solid body using AP214 or AP242. If the file still will not open here, a machine shop can usually open it in its own software, so you can still request a quote.

Capabilities

Capabilities that use STEP files

Send a STEP file to get quotes for any of these processes.

CNC Machining5-Axis MachiningCNC TurningSwiss MachiningSheet Metal FabricationInjection MoldingDie CastingEDM & Wire EDM

Free tools

More free tools and charts

Free STL file viewerCheck 3D printing files before you print or quote.Free DXF and DWG viewerSee the size and cut length of flat drawings.CNC machining tolerance chartStandard tolerances by feature, plus ISO 2768 classes.

Frequently Asked Questions

Is this STEP viewer free?
Yes. There is no account, no install, and no limit on how many files you open. Files up to 25 MB are supported.
Is my STEP file uploaded?
No. The file is read and displayed by your browser on your computer. It is only uploaded if you click Get a quote and then submit the request.
What is the difference between .step and .stp?
None. They are two file extensions for the same format, defined by ISO 10303.
Can I measure a part in the viewer?
The viewer shows the part's overall size along the model's X, Y, and Z axes, plus its volume, in millimeters or inches. The readout is labeled approximate, so treat it as a quick check, and confirm critical dimensions in your CAD program or on a drawing.
Can I open a SolidWorks or Fusion file here?
Not directly. Native formats such as .sldprt, .f3d, and .ipt need to be exported first. Use File > Save As or Export in your CAD program and choose STEP.
Which STEP version should I export?
AP214 or AP242 works for most shops. AP242 is the newest of the three and can carry manufacturing information. AP203 is older but still widely read.

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