| .T04 | Tobias Svensson | 3D Image Files | Top 4 Compressed Data File | top 4 | Unknown Developer |
| .T3D | Epic Games | 3D Image Files | Unreal Engine 3D Object File | Unreal Tournament | Epic Games |
| .TDDD | Impulse | 3D Image Files | Imagine Object File Format | Impulse Imagine | Impulse |
| .TDIM | Unknown Developer | 3D Image Files | Digital F/X Image Format | XnView MP | XnSoft |
| .TER | Planetside Software | 3D Image Files | Terragen Terrain File | Planetside Software Terragen | Planetside Software |
| .TGM | Open Source | 3D Image Files | Nem's Mega 3D Terrain Generator | Nem's Mega 3D Terrain Generator | Open Source |
| .THL | Individual Software Inc. | 3D Image Files | Total 3D Home Design File | Total 3D Home Design Deluxe | Individual Software Inc. |
| .THUMBDATA3 | Google | 3D Image Files | Google Android Thumbnail Database | Google Android | Google |
| .THUMBDATA5 | Google | 3D Image Files | Google Android Thumbnail Database | Google Android | Google |
| .TIN | Bentley Systems | 3D Image Files | Bentley GEOPAK Environmental Modeling Systems Data | GEOPAK Civil Engineering Suite | Bentley Systems |
| .TMD | SoftMaker Software | 3D Image Files | TextMaker Document | Softmaker Office | SoftMaker Software |
| .TME | DAZ 3D | 3D Image Files | Bryce Time File | DAZ 3D Bryce | DAZ 3D |
| .TML | Odetics Broadcast | 3D Image Files | AIRO Timeline File Format | AIRO | Odetics Broadcast |
| .TMO | Yu Higuchi | 3D Image Files | 3DCG Animation And Pose File | MikuMikuDance | Yu Higuchi |
| .TMP | Mozilla | 3D Image Files | General Temporary File | Internet Explorer | Microsoft Corporation |
| .TNL | Unknown Developer | 3D Image Files | Thumbnail Image Format | Unknown Software | Unknown Developer |
| .TOP | KTH Royal Institute of Technology | 3D Image Files | Gromacs Topology File | Gromacs | KTH Royal Institute of Technology |
| .TOTAL COMMANDER BUTTON BAR SETTINGS | Interscape | 3D Image Files | Total Commander Button Bar Settings | Total Commander | Ghisler Software GmbH |
| .TPS | TiePie engineering | 3D Image Files | Multi Channel Measurement File | Multi Channel | TiePie engineering |
| .TRI | Singular Inversions | 3D Image Files | FaceGen Polygonal Model File | The Elder Scrolls IV: Oblivion | Bethesda Softworks |
| .TRU | Original Basic | 3D Image Files | True Basic Source | True Basic Bronze Edition | Original Basic |
| .TSO | Siemens AG | 3D Image Files | NX2 File 3D Faceted Spacial Volume Data | Siemens PLM NX | Siemens PLM Software |
| .TVP | NVIDIA | 3D Image Files | NVIDIA Graphic Card Update File | NVIDIA Graphics Driver | NVIDIA |
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