3D File Formats Explained: STL vs OBJ vs PLY vs GLB vs 3MF
Download a 3D model and you will quickly hit an alphabet soup of extensions: .stl, .obj, .ply, .glb, .3mf. They all describe a 3D shape, but they are built for very different jobs - and using the wrong one is why a model refuses to slice, loses its colours, or will not load in a web viewer.
This guide explains what each format actually stores, when to use it, and how to convert between them in seconds.
The one thing they have in common
All five are mesh formats: they describe a surface as a web of points (vertices) joined into triangles (faces). What differs is how much extra information rides along - colour, texture, materials, units, print settings - and how the data is packed.
STL - the 3D printing standard
STL stores nothing but raw triangles: pure surface geometry, no colour, no units, no metadata. That simplicity is exactly why it became the universal language of 3D printing - practically every slicer and printer accepts it. Use STL when your goal is to print, and you do not need colour or materials.
OBJ - the editing and rendering workhorse
OBJ is a widely supported text format that stores geometry plus texture coordinates and normals, and can reference a separate materials file. It is the common interchange format between modelling and rendering tools. Use OBJ when you are editing, texturing or rendering a model rather than printing it.
PLY - the scanning and research format
PLY (the Stanford Triangle Format) can carry per-vertex colour and custom attributes, which is why it is the standard output of 3D scanners and photogrammetry. Use PLY when you are working with scanned data or point-coloured meshes.
GLB - the web and AR format
GLB is the binary form of glTF, often called "the JPEG of 3D". It packs geometry, materials, textures and scene data into one compact, self-contained file that loads fast in browsers, AR viewers and game engines. Use GLB for anything that will be viewed online or in augmented reality.
3MF - the modern printing format
3MF was designed to replace STL. It stores the mesh plus colour, materials, units and print settings in a compact package, fixing many of STL's limitations. Use 3MF for modern multi-colour or multi-material printing when your slicer supports it.
Quick reference
- Printing: STL (universal) or 3MF (modern, with colour and settings)
- Editing / rendering: OBJ
- Scanning / research: PLY (and the academic OFF format)
- Web / AR / real-time: GLB
How to convert between them
You rarely get the format you need on the first try - a printer wants STL, a web viewer wants GLB, an editor wants OBJ. Converting is quick and keeps the geometry intact:
See the full set on the 3D & CAD tools page.
A note on what gets lost
Because the formats store different things, some conversions are naturally lossy. Going from a colourful GLB to STL drops colour and materials, because STL has no way to store them - the shape is preserved perfectly, but the paint is not. Converting the other direction is fine. As a rule: geometry always survives; extras only survive if the target format supports them.
Is it private to convert 3D models online?
With PrivConvert, yes. Every conversion runs in an isolated, network-free environment, entirely in memory:
- Your model is processed in server memory and never written to disk
- It is deleted the instant your download is ready
- All transfers use HTTPS encryption
- No account, no tracking, no file storage
Learn more on our why PrivConvert and security pages.