# Mesh CAD Formats: STL, OBJ, 3MF, glTF and GLB

Inspect STL, OBJ, 3MF and static glTF or GLB meshes. Units and closure differ by format. Mesh measurements are approximate and are not precise STEP solids.

STL, OBJ, 3MF, glTF and GLB are triangle meshes. They are not the same format, and they do not share one unit rule. None of them is a precise CAD solid. A mesh cannot be converted back into the original STEP surfaces or feature tree.

## Open the mesh you have

| Format | Where to open it | Units on this site | Conversion |
|---|---|---|---|
| STL | [STL viewer](https://www.cadprops.com/tools/stl-viewer/index.md) | Assumed millimetres. No reliable unit field | [STL to OBJ](https://www.cadprops.com/tools/stl-to-obj/index.md) |
| OBJ | [OBJ viewer](https://www.cadprops.com/tools/obj-viewer/index.md) | Assumed millimetres | [OBJ to STL](https://www.cadprops.com/tools/obj-to-stl/index.md) |
| 3MF | [3MF viewer](https://www.cadprops.com/tools/3mf-viewer/index.md) | Declared supported units converted to millimetres. Core mesh only | No public 3MF-input conversion |
| glTF / GLB | [glTF viewer](https://www.cadprops.com/tools/gltf-viewer/index.md) and [GLB viewer](https://www.cadprops.com/tools/glb-viewer/index.md) | glTF metres normalized to millimetres. Local resources must travel with the file | No public glTF-input conversion |

STEP can be tessellated outward: [STEP to STL](https://www.cadprops.com/tools/step-to-stl/index.md), [STEP to OBJ](https://www.cadprops.com/tools/step-to-obj/index.md), [STEP to 3MF](https://www.cadprops.com/tools/step-to-3mf/index.md), [STEP to glTF](https://www.cadprops.com/tools/step-to-gltf/index.md) and [STEP to GLB](https://www.cadprops.com/tools/step-to-glb/index.md). Those outputs are meshes. Check a known dimension in the receiving program.

## Measurement limits

Mesh dimensions and area are approximate. Volume and density-based mass require a closed, consistent mesh; otherwise they stay unavailable rather than becoming zero. [Watertight meshes](https://www.cadprops.com/guides/watertight-cad-mesh/index.md) and [STL volume](https://www.cadprops.com/guides/why-stl-volume-is-zero/index.md) explain that status. [STL units](https://www.cadprops.com/guides/stl-files-have-units/index.md) covers the 25.4 inch/millimetre trap. [Tessellation](https://www.cadprops.com/guides/cad-tessellation/index.md) is why a finer mesh is still not B-Rep.

3MF here is core geometry, not a print profile. glTF animations and remote textures are not fetched. A ZIP may carry a glTF scene with its local buffers; the package limit is 50 entries and 100 MiB expanded.

## Do not mix these up with solids

[STEP vs STL](https://www.cadprops.com/guides/step-vs-stl/index.md) and [3MF vs STL](https://www.cadprops.com/guides/3mf-vs-stl/index.md) are the format comparisons. For precise volume, start from STEP or another enabled B-Rep input on the [STEP hub](https://www.cadprops.com/step/index.md). Rhino 3DM, DWG and DXF are not mesh uploads and are not enabled; see [3DM](https://www.cadprops.com/guides/open-3dm-without-rhino/index.md) and [DWG or DXF](https://www.cadprops.com/guides/open-dwg-dxf-without-autocad/index.md).

Samples for a known-good mesh are listed in the [format matrix](https://www.cadprops.com/supported-formats/index.md).

HTML page: https://www.cadprops.com/mesh-formats/