| tmtheme | TextMate Theme |
| tmv | TimeMap Visual Data |
| tmw | Translation Memory Data |
| tmw | Twinmotion Data |
| tmx | Arbortext Editor Custom Input Data |
| tmx | Tiled Tile Map XML |
| tmy | Typical Meteorological Year Data |
| tmz | Medigraph Compressed Database |
| tmzip | Theme Manager Zip Package |
| tna | Topocad Net Adjustment |
| tnd | CAS-Hydro Tree-node Definition File |
| tnd | TranEd v2 File |
| tnef | Transport Neutral Encapsulation Format |
| tnf | Transport Neutral Encapsulation Format |
| tnfo | SpyBot Search and Destroy TNFO Data |
| tni | TexNet32 Database Index |
| tnj | CapturePost TimeStone Neo Job Data |
| tnk | Nimbus 7 SAMS Data |
| tnt | TNT Data File |
| tnt | TurnTool 3D Model |
| tnx | PageTech PCLTool Text Extraction File |
| tob | Zemax Object Data |
| toc | Eudora Addressbook TOC |
| tocf | Qualcomm Eudora for Mac TOC Data |
| tof | Mr. Photo Thumbnail |
| tog | TouchDesigner Geometry Data |
| tol | AOL Tool |
| tom | Medigraph Database |
| ton | FMS32 Protocol Data |
| tool | Apple Terminal Data |
