Quick answer
The right 3D file format depends on the job. Use STL or 3MF for 3D printing, glTF or GLB for websites and AR, STEP to share exact CAD geometry, IFC for building models, FBX for animated assets and PLY for 3D scans. The biggest difference is between mesh formats, which store triangles, and CAD formats, which store exact surfaces.
Mesh vs CAD: the difference that matters most
Almost every 3D format belongs to one of two families. Knowing which one your file is in tells you what you can do with it.
- Mesh formats (STL, OBJ, glTF, FBX, 3MF, PLY, USDZ) describe a surface as many small, flat triangles. 3D printers, games, websites and AR apps all work with meshes. Curves are approximated, so a circle is really a polygon with many sides.
- CAD formats (STEP, IGES, BREP) store an exact boundary representation, or B-rep: true mathematical surfaces and edges. A drilled hole stays a perfect cylinder at any zoom. Engineers need this to machine, measure and edit parts.
- BIM formats (IFC) add meaning on top of the geometry. A wall knows it is a wall, which storey it is on and what it is made of.
Turning a CAD model into a mesh is routine. Going the other way is not: a mesh saved in a CAD format is still a set of flat faces, not an editable solid.
3D file formats compared
This table shows what each format can hold. Individual files may use less: an FBX exported without animation has none, for example.
| Format | Full name | Typical use | Geometry | Materials and textures | Animation | Assemblies and hierarchy |
|---|---|---|---|---|---|---|
| STL (.stl) | Stereolithography | 3D printing | Mesh (triangles) | None | No | No |
| OBJ (.obj, .mtl) | Wavefront OBJ | Moving meshes between 3D apps, rendering | Mesh (polygons) | Basic materials and textures, in a separate .mtl file | No | Named groups only |
| glTF / GLB (.gltf, .glb) | GL Transmission Format 2.0 | Websites, online stores, AR, real-time apps | Mesh | PBR materials and textures | Yes | Yes |
| FBX (.fbx) | Filmbox (Autodesk) | Animation, games, film and VFX | Mesh | Materials and textures | Yes, with skeletons | Yes |
| STEP (.step, .stp) | Standard for the Exchange of Product model data (ISO 10303) | Sharing CAD between programs, manufacturing | Exact B-rep solids and surfaces | Colours only | No | Yes, full assemblies |
| IGES (.iges, .igs) | Initial Graphics Exchange Specification | Older CAD systems, surface models | Exact B-rep, mostly surfaces | Colours only | No | Limited |
| IFC (.ifc) | Industry Foundation Classes (ISO 16739) | BIM for architecture and construction | Exact solids or meshes, plus object data | Colours and surface styles | No | Yes: site, building, storey, element |
| 3MF (.3mf) | 3D Manufacturing Format | Modern 3D printing | Mesh (triangles) | Colours and materials; textures through an extension | No | Yes, several objects |
| PLY (.ply) | Polygon File Format (Stanford) | 3D scans and point clouds | Mesh or point cloud | Colour per vertex | No | No |
| USDZ (.usdz) | Universal Scene Description, zipped | AR on iPhone and iPad | Mesh | PBR materials and textures | Yes | Yes |
Mesh means the surface is stored as triangles or polygons. Exact B-rep means it is stored as precise curved surfaces, the way CAD software models it.
Which 3D file format should I use?
Use the format your next tool expects. When you have a free choice, this is a good starting point.
| Your job | Best format | Why |
|---|---|---|
| 3D printing | 3MF, or STL | Every slicer reads STL. 3MF also keeps units, colours and several parts in one file. |
| Websites, online stores and AR | GLB (USDZ for iPhone AR) | One compact file with PBR materials and animation. Apple’s AR Quick Look needs USDZ instead. |
| Sending CAD to another company | STEP | Exact geometry and the full assembly, readable by almost every CAD program. |
| Working with older CAD systems | IGES | Only when the other side asks for it. Otherwise, send STEP. |
| Buildings and infrastructure (BIM) | IFC | An open standard that keeps building elements, storeys and their properties. |
| Animation and games | FBX to exchange, GLB to deliver | FBX is what most animation tools and game engines trade. GLB is the open choice for real-time delivery. |
| 3D scans | PLY | Holds dense meshes, point clouds and per-vertex colour straight from the scanner. |
| Moving a mesh between 3D apps | OBJ or glTF | OBJ is simple and nearly universal. glTF also keeps PBR materials, hierarchy and animation. |
Not sure what your file contains?
Open it in the 3D Viewer to see its parts, triangle count and file size. Nothing is uploaded.
The main 3D file formats in plain words
STL
STL is the oldest and most widely supported 3D printing format. It stores a surface as a list of triangles and nothing else: no colour in the base specification, no materials and no units. Every slicer reads it, which is why it is still everywhere.
Open one in the STL viewer, or make it web-ready with STL to GLB.
OBJ
OBJ is a plain-text mesh format from Wavefront that almost every 3D program can read and write. Materials live in a separate .mtl file, and textures are separate images. Keep them all together, or the model loses its colours.
The OBJ viewer loads the .obj, .mtl and textures when you drop them in together.
glTF and GLB
glTF 2.0 is an open standard from the Khronos Group, built to deliver 3D models quickly to apps and browsers. It stores meshes, PBR materials, textures, animation and the scene hierarchy. A .gltf file is JSON with separate data files, while a .glb packs everything into one binary file.
Our glTF vs GLB guide explains when to use each, and the glTF viewer opens both.
FBX
FBX is Autodesk’s format for moving animated assets between programs such as Maya, 3ds Max, Blender, Unity and Unreal Engine. It carries skeletons, skinning, animation, materials and textures. The specification is not public, so support varies from one program to the next.
Open it in the FBX viewer, or convert FBX to GLB for the web.
STEP
STEP (ISO 10303) is the standard way to send CAD models between different CAD programs. It stores exact solids and surfaces, the assembly tree, part names and, usually, colours.
Read how to open a STEP file, or go straight to the STEP viewer.
IGES
IGES is a CAD exchange format that dates from the early 1980s. It handles surfaces well but solids and assemblies less reliably, so STEP has replaced it for most work. You still meet it with older CAD systems and surface models.
Open it in the IGES viewer.
IFC
IFC (ISO 16739) is the open format for building information modelling (BIM), maintained by buildingSMART. It stores real building elements, such as walls, slabs, doors and pipes, with their properties and the storey they belong to.
Open one in the IFC viewer, or read our guide to viewing IFC files online.
3MF
3MF is a 3D printing format from the 3MF Consortium, designed to fill STL’s gaps. It records units, colours, materials and several objects in one file. It is a ZIP package, so it is often smaller than the same model saved as STL.
Try the 3MF viewer.
PLY
PLY, the Polygon File Format, was created at Stanford University for storing 3D scans. It holds meshes or bare point clouds, often with a colour for every vertex. Many 3D scanners and photogrammetry apps export it.
Open it in the PLY viewer, or convert PLY to STL to print a scan.
USDZ
USDZ packs a Universal Scene Description (USD) scene, a format that began at Pixar, into a single file. Apple uses it for AR Quick Look, the AR viewer built into iPhone and iPad.
You can make one from a GLB with GLB to USDZ.
How to convert between 3D formats
The free 3D Converter turns the formats the viewer opens into GLB, glTF, OBJ, STL, PLY or USDZ, several files at a time. Common conversions include:
- STEP to STL to 3D print a CAD part
- FBX to GLB to put an animated model on the web
- OBJ to GLB to pack a mesh, its materials and textures into one file
- IFC to GLB to share a building model with people who do not use BIM software
- STL to OBJ to bring a print file into a 3D modelling app
Before you convert, the converter tells you what the target format cannot hold, such as materials, textures, animation or part hierarchy. FBX, STEP and IFC can be opened and converted, but not written.
Keep your original file. A converted copy can lose materials, animation or exact CAD geometry, and you cannot get them back from it.
What about other 3D formats?
There are dozens more, most of them tied to one program or an older pipeline. The 3D Viewer also opens:
- CAD and design files: BREP, Rhino (.3dm), FreeCAD (.fcstd) and AMF.
- BIM: dotbim (.bim) alongside IFC.
- Older 3D and game formats: Collada (.dae), 3DS, LightWave (.lwo), DirectX (.x), OFF, VRML (.wrl), MilkShape (.ms3d), Quake (.md2, .md3) and more.
- Archives: a ZIP file or a whole folder, with textures and other companion files loaded alongside the model.
That makes 30+ formats in all, each opened on your own device.
Frequently asked questions
What is the most widely supported 3D file format?
It depends on the field. STL is read by virtually every 3D printing tool, OBJ by nearly every 3D modelling program, and glTF or GLB by web and AR viewers. In CAD, STEP is the format almost every program can exchange.
What is the difference between a mesh and a CAD file?
A mesh stores a surface as flat triangles, which is ideal for display, games and 3D printing. A CAD file such as STEP stores exact curved surfaces and solids, which engineers need to measure, machine and edit a design.
Can I convert STL to STEP?
Not in a useful way. An STL holds only triangles, so a STEP made from it is still faceted and cannot be edited like a real CAD solid. MicroPlugins converts CAD to mesh, such as STEP to STL, OBJ or GLB, but not back.
Which 3D format is best for websites?
GLB, the single-file form of glTF 2.0. It keeps PBR materials, textures and animation in one compact file. Read glTF vs GLB for the details and how to reduce GLB file size before you publish.
Is 3MF better than STL for 3D printing?
For most prints, yes, if your slicer supports it. 3MF records units, colours, materials and several objects, and it is often smaller. STL is still the safest choice when you do not know which software will open the file.
How can I open a 3D file without installing software?
Drop it onto the free MicroPlugins 3D Viewer. It opens 30+ formats, including STL, OBJ, glTF, FBX, STEP, IGES and IFC, in your browser. The file is read on your device and is never uploaded.
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