STEP to GLB converter. CAD files, web-ready.
Drop a .step or .stp file and get a GLB a web page can show, tessellated on your device with part names, colors and real-world size kept.
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No STEP file at hand?
What a STEP file is, and why a web page cannot show it
STEP is the neutral format CAD systems use to exchange exact geometry; a browser draws triangles, so a STEP file has to be tessellated before it can go on a product page.
STEP (ISO 10303, files ending in .step or .stp) stores a part the way your CAD system does: as a boundary representation, B-rep for short. Every face is an exact mathematical surface — a plane, a cylinder, a NURBS patch — trimmed by its edges. That precision is why manufacturers send STEP to suppliers, CNC shops and customers, and why SolidWorks, Inventor, Creo, CATIA, NX, Fusion and Onshape all export it. The common flavors are AP203, AP214 (which adds colors and layers) and AP242 (which adds product manufacturing information such as tolerances).
A web page, a 3D configurator or a phone in AR mode cannot draw an exact surface. WebGL draws triangles, and the web's 3D file format, glTF (and its single-file binary form, GLB), holds triangles, materials and a node tree. No browser opens STEP natively. Before a CAD model can go online, every surface has to be approximated by triangles — tessellated — and the result written as GLB, in meters, with the colors a shopper should see.
That approximation is a trade-off you control in principle: a tighter tolerance follows curves more closely and costs more triangles, and triangles are what make a model slow to download and render. A product page needs a model that looks right at the distance a shopper views it, not one that matches the CAD to a micron.
How to convert STEP to GLB
Five steps take a STEP file to a GLB a browser can show. This is the general method, and what this tool does at each step.
01Read the B-rep and its assembly
A STEP reader rebuilds the exact solids and surfaces, and the assembly: which parts there are, how many times each is used, and where each instance is placed.
This tool: reads AP203, AP214 and AP242 files with OpenCascade, the open-source CAD kernel, compiled to WebAssembly. Every part instance is placed where the assembly puts it.
02Tessellate every surface
Each face is cut into triangles within a tolerance: a chordal deviation (how far a triangle may sit from the true surface) and an angular deviation (how sharply neighboring triangles may bend). Tighter means smoother curves and more triangles.
This tool: a chordal tolerance of 0.1% of the model's average bounding-box size and an angular tolerance of 0.5 radians (about 29°). It is fixed, not adjustable.
03Convert the units
STEP files declare their unit — millimeters for most CAD, sometimes inches. glTF is always meters, so a model exported in millimeters must be scaled by 0.001 or it comes out a thousand times too big.
This tool: reads the file's declared unit, converts it to millimeters, then scales by 0.001 to meters. A 1,200 mm table is 1.2 m in the GLB.
04Carry names and colors
Part names let a configurator find a part ("Top", "Leg") to swap or recolor it. STEP colors can sit on a whole body or on single faces; a good conversion turns each distinct color into a material.
This tool: names each mesh after its part, and makes one non-metallic material per distinct body or face color, named by its hex value. Parts without a color get a neutral grey.
05Optimize and write the GLB
Tessellated CAD carries duplicate vertices and uncompressed data. Merging, indexing and compressing it can cut the file to a fraction before it ships.
This tool: merges duplicate data, indexes vertices, removes what nothing uses, then applies Meshopt compression (Web preset) or writes plain glTF 2.0 geometry (Max compatibility).
STEP and GLB, side by side
They solve different problems: STEP keeps engineering truth, GLB is built to be downloaded and drawn fast.
| Aspect | STEP (.step, .stp) | GLB |
|---|---|---|
| Geometry | Exact B-rep surfaces: planes, cylinders, NURBS | Triangles |
| Units | Declared in the file (mm, inch, …) | Always meters |
| Structure | Assemblies of parts with placements | A node tree (this tool writes one node per part) |
| Appearance | Optional colors per body or face | PBR materials and embedded textures |
| Manufacturing data | Tolerances and annotations (AP242) | None |
| Opens in a browser | No | Yes: three.js, Babylon.js, <model-viewer>, Android Scene Viewer |
| Made for | Exchanging designs between CAD systems | Showing products on the web and in AR |
Before you export the STEP file
Four settings in your CAD decide how good the GLB looks and how heavy it is.
Export colors
Choose AP214 or AP242 and turn on colors or appearances in the export options. AP203 files usually carry no color, so every part comes out grey.
Leave out what nobody sees
Fasteners, internal mechanisms and threads can be most of the triangles and none of the sale. Suppress or hide them before exporting a model for a product page.
Export solids or surfaces
Sketches, wireframe and drawing annotations have no surface to tessellate. A file with only those converts to nothing.
Check the up axis
STEP declares no "up". This tool keeps your CAD's axes, and web viewers treat Y as up, so a Z-up model shows lying on its back. Rotate it in your CAD before export, or in the viewer you use.
Questions about the STEP to GLB converter.
What it does, what it leaves to you, and what it costs.
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