Convert GLB to STEP
GLB is the format 3D on the web is delivered in. STEP is the format engineering runs on. Going from one to the other means turning a surface made of triangles into a solid made of faces, which this does in your browser — including the merge that keeps the file small enough to open. Two things catch people: GLB is measured in metres, and the smooth surfaces you see in a GLB viewer are not smooth underneath.
Drag a 3D file here, or.
This page is set up for GLB files. Other formats we can read work here too.
The file is read on your own computer. It is never uploaded.
Your file is read by your own browser and never sent to a server. There is no upload, no account and no copy of your model anywhere but on your computer.
The scale trap, first, because it ruins the most files
glTF and GLB are defined in metres. That is in the specification, and every web viewer honours it. CAD and 3D printing work in millimetres. So a 40 millimetre bracket is stored in a GLB as the number 0.04, and converting it without touching the units gives a CAD file claiming a part 0.04 millimetres wide — a fortieth of a millimetre, invisible on screen.
The unit boxes on this page start correctly for this pair: metres in, millimetres out. Read the width, depth and height under the 3D view before you convert. If they match the real object, the file will be right.
The smooth surfaces are shading, not shape
A GLB stores a normal at every corner, which is what tells a renderer to blend the light across a face so a low-polygon cylinder looks round. It is a trick for the eye and it works beautifully. Underneath, the geometry is still flat strips.
CAD has no equivalent. A face in a STEP file is a real surface with a real shape, and there is nothing to store a shading hint in. So the STEP shows you what was actually there: a twelve-sided cylinder looks like a twelve-sided cylinder, and it always was one. What you get is a faceted solid — real enough to cut, measure and assemble, and not a parametric model with features you can edit.
This surprises people more than any other part of the conversion, so it is worth checking in the 3D view on this page before you convert. The viewport here rebuilds the shading from the geometry rather than trusting the file, which means what you see is what the CAD file will contain.
What the merge does to a web model
Models made for the web are built to be light, so flat surfaces are already made of as few triangles as possible: a wall is two triangles, not two hundred. That means the merge has less to do than on a CAD-exported STL, but it still halves the face count on anything with flat sides, and it matters most where it matters most — a large flat panel becomes one face instead of two, and then behaves like a face when you click it in CAD.
On a model that is mostly curved, nothing merges and the STEP file gets one face per triangle. Watch the report under the download button; if the count is high, the reduction box on this page will bring it down.
Textures, materials and scenes
A GLB carries its textures and materials inside it. None of them survive into STEP, and none of them should: a CAD file has no concept of an image mapped onto a surface. The geometry is what crosses over.
A GLB can also hold a whole scene — several meshes, arranged by a hierarchy of transforms. Every mesh is listed above the 3D view with its own name, already in its final position, and each becomes a separate solid inside the STEP file. Isolate one if the scene has more in it than you need.
What survives, and what does not
Kept in the STEP file
- The geometry, exactly as it is in the file, positioned as the scene arranged it
- The real size, once the metres-to-millimetres conversion is applied
- Separate meshes, as separate named solids in one STEP file
- Flat regions, merged into single faces
Lost on the way
- Textures, materials and colours — a CAD file has nowhere to put any of them
- Smooth shading, which was a renderer’s trick over flat geometry
- Animation, cameras, lights and anything else in the scene that is not a surface
How to convert GLB to STEP
Drop the .glb or .gltf in
A .glb holds everything in one file. A .gltf usually points at a .bin beside it — drop both together.
Check metres in, millimetres out
That is how the boxes start, because glTF is defined in metres. The measurements under the 3D view should now be the real size of the object.
Look at the model before converting
The viewport shows the real geometry rather than the file’s shading. If a curve looks faceted here, it will be faceted in the STEP file, and no setting changes that.
Convert and check the face count
The report under the download button says how many triangles became how many faces. A number in the thousands opens fine; a number in the hundreds of thousands means reducing first.
GLB and STEP compared
| Property | GLB.glb | STEP.step .stp |
|---|---|---|
| File contents | One binary file: a small header, the same JSON as glTF, then all the buffers and images. | Plain text in the ISO 10303-21 exchange form. Readable, and enormous. |
| Geometry | Triangles, with skinning weights and animation channels alongside them. | Exact surfaces: planes, cylinders, cones, spheres, NURBS. Not triangles. |
| Units | Metres, fixed by the specification. | Recorded in the file, as a full unit and tolerance context. |
| Colour and texture | Full physically based materials, with the texture images packed inside the file. | Colour per face or per solid, through the AP214 and AP242 styling entities. |
| Separate objects | A scene graph of named nodes, each with its own position and rotation. | An assembly tree of named parts, each with its own placement. |
| Published by | The Khronos Group, 2015, as the single-file packaging of glTF. | ISO 10303, from 1994. AP242 is the current application protocol. |
| Written by | Blender, Sketchfab, Substance Painter, and every tool that ships models to the web. | SolidWorks, Fusion 360, Inventor, CATIA, FreeCAD, Onshape — every serious CAD program. |
Questions
- My part came into CAD 1000 times too small.
- The unit. glTF and GLB are defined in metres and CAD works in millimetres. Set the first box to metres and the second to millimetres — which is how this page starts — and check the measurements under the 3D view before converting.
- The model looked smooth online and came out faceted.
- The smoothness was shading. A GLB stores a normal at each corner so a renderer can blend light across flat faces; the geometry underneath was always flat. STEP stores real surfaces and has nowhere to keep a shading hint, so you see what was there.
- Is this a real CAD model I can edit?
- It is a real solid: your CAD program can cut it, add to it, measure it, section it and put it in an assembly. It is not a parametric model. There is no sketch to change, no extrude to edit and no dimension to type a new number into, because none of that is in a mesh to be recovered. If you need those, the model has to be drawn again from measurements.
- Can I keep the texture?
- No. STEP has no concept of an image on a surface. If you want the texture, convert to OBJ or keep the GLB — this site does both — and use the STEP for the engineering work.
- Does my file get uploaded?
- No. The whole conversion runs inside your browser, and nothing is sent anywhere. That matters more here than on most pages: a part being taken into CAD is usually somebody’s product.