How do I open a SolidWorks or Inventor part?

SLDPRT, SLDASM, IPT and IAM are closed native formats that only their own programs read. In SolidWorks use File → Save As and choose STEP AP214 or AP242; in Inventor use File → Export → CAD Format → STEP. The resulting file opens here with its assembly tree and part names.

What units are the dimensions shown in?

In the units the file was written in: STEP keeps its length unit next to the geometry, IGES in its header. The mm / in switch above the size converts every number. BREP files carry no units, so their numbers are shown as millimeters. The STL is always saved in millimeters, which is what slicers expect.

How accurate are the dimensions?

Sizes are measured on the model's triangulated surface. On flat faces they match the CAD dimensions exactly; on cylinders and fillets they can come out a fraction of a percent smaller, because arcs are built from chords with a tolerance of about 0.05% of the size of the whole model. That is enough to check a part against its drawing, not for metrology.

Why is the model gray when it had colors in CAD?

Only the colors written in the file are shown. STEP AP203 stores no colors at all, and AP214 and AP242 carry them only if color export was turned on. Parts without a color are drawn in neutral gray.

What if a large assembly does not open?

The browser gives a tab at most 2 GB of memory for reading the model, and a phone noticeably less. Assemblies of tens of megabytes are best opened on a computer with other tabs closed. If that is still not enough, export the sub-assembly you need from your CAD program as a separate STEP file. How much fits exactly depends on the device.

Are the dimensions and tolerances (PMI) of an AP242 file shown?

No: the tool shows geometry — solids and surfaces. PMI annotations such as dimensions, geometric tolerances and datums are not drawn. The helper surfaces they are attached to appear as separate surface parts; you can hide them in the tree.

STEP and IGES Viewer Online

STEP is the exchange format for 3D models (ISO 10303): every serious CAD system saves it, and suppliers, designers and model libraries send parts in it. Inside there is no triangle mesh but exact boundary geometry — planes, cylinders, spline surfaces — so viewing it takes a geometry kernel. Here that kernel is Open CASCADE Technology compiled to WebAssembly: the model is built in the browser, with no CAD program installed. STEP AP203, AP214 and AP242 open, as do IGES files, including surface models, and BREP files from FreeCAD. An assembly appears as a tree with the part names and colors from the file, and sizes are given in the units the model was written in: millimeters or inches.

How to use it

3 steps

Upload the model

Drop a .step, .stp, .igs or .iges file — or a ZIP archive with the model inside. The format is recognized by its content, so a file without an extension works too.

Explore the assembly

Rotate the model, switch standard views, hide parts in the tree and read the size of the whole model and of the selected part.

Take the STL

Download the visible parts or one selected part as STL — a file every 3D printing slicer understands.

Open a CAD model in your browser and save it as STL

Drop a file here

STEP (.step, .stp), IGES (.igs, .iges), BREP — or a ZIP archive with the model ·

The model is read by occt-import-js · Open CASCADE Technology (LGPL-2.1).

💡 Want us to improve this tool just for you?

We can! Just send us a quick message with your idea. If you'd like to discuss it in detail, leave your email and we'll get back to you. You can stay anonymous.

How do you rate this tool?

Thank you for your rating!

Change my rating

Want to leave a comment?

Want to share more? Leave a comment!

Thank you! Your comment will appear after moderation.

Who is this tool for?

🩹 File recovery

Published 05 Nov 2026 Author: The Supreme