| 3dd | Neuroscan 3D Coordinates Data |
| 3de | 3Data Expert Data |
| 3dh | SeisWorks Horizontal Time-slice Format File |
| 3di | Altair FEKO 3D Artwork Data |
| 3dmap | Catia 3DMAP File |
| 3dmap | Metaio SDK 3D Map |
| 3dmbak | Rhino 3D Model Backup |
| 3don | Scrutinize 3D Mesh Data |
| 3dr | 3DMark Results Data |
| 3drep | Catia 3D Geometry Data |
| 3dtiles | Cesium 3D Tiles Database |
| 3dv | SeisWorks Vertical Time-slice Format File |
| 3dvs | 3DViewStation Document |
| 3dw | 3D World Studio Model |
| 3dweb | pCon.planner 3dWeb Data |
| 3dxmj | 3D-XplorMath-J Visualization Data |
| 3es | 3rd Eye Scene Data |
| 3fk | Bemio Froud-Krylof Data |
| 3fx | CorelDRAW Corel Chart 3D Effect Data |
| 3gf | BlackVue Dashcam Accelerometer Data |
| 3gt | 3D Graphic Tools Model |
| 3h | Advent 3B2 Tag Header |
| 3map | Thoughtograph Mind Map Data |
| 3mx | ContextCapture 3D Multiresolution Mesh eXchange Data |
| 3mxb | ContextCapture Binary 3MX Data |
| 3ox | 3Shape Order Exchange Format Data |
| 3oxz | 3Shape Order Exchange Format Data |
| 3pe | Intuit TurboTax 2008 Form |
| 3rf | Arbortext Advanced Print Publisher Cross Reference Data |
| 3sc | Bemio Scattering Data |
| 3sm | ContextCapture Scalable Mesh |
| 3th | 3D Movie Maker Thumbnail Data |
| 3ws | CityEngine Web Scene |
| 3x5 | 3x5 Knowledge Base Data |
| 4a3 | STABCAL Data |