| tmd | TrueMap Surface Data |
| tmdb | TaskMerlin Database |
| tme | Bryce Time Data |
| tmg | The Master Genealogist Data |
| tml | DB/TextWorks Thesaurus Maintenance Lock |
| tmlanguage | TextMate Language Grammar Data |
| tmm | TimeMap Metadata |
| tmn | Tmin Input File |
| tmpl | Xfire User Interface Template |
| tmprtf | LexisNexis TimeMap Portable Format Data |
| tmq | TestMaster Questions Data |
| tmr | Free Countdown Timer Backup File |
| tms | Tableau Map Source |
| tmtheme | TextMate Theme |
| tmw | Translation Memory 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 | TranEd v2 File |
| tnd | CAS-Hydro Tree-node Definition File |
| tnef | Transport Neutral Encapsulation Format |
| tnf | Transport Neutral Encapsulation Format |
| tni | TexNet32 Database Index |
| tnj | CapturePost TimeStone Neo Job Data |
| tnk | Nimbus 7 SAMS Data File |
| tnt | TNT Data File |
| tnx | PageTech PCLTool Text Extraction File |
| tob | Zemax Object Data |
| toc | Eudora Addressbook TOC |
| tof | Mr. Photo Thumbnail |
| tog | TouchDesigner Geometry Data |
| ton | FMS32 Protocol Data |
| top | E-Sword v8 Topic Note |