| trc | True BASIC Compiled Program |
| trdf | Apache Jena RDF Thrift Data |
| tres | Godot Engine Text Resource Data |
| trs | WinDev HyperFileSQL Transaction Log |
| tru | True BASIC Source Code |
| trw | Turbo Debugger for Windows Session-state Settings |
| trx | WinDev HyperFileSQL Transaction TRX Log |
| ts | Turbulenz Script |
| tscn | Godot Engine Text Scene Data |
| tsf | ProWorx NXT Symbol File |
| tsn | RatLab Training SFA Network Data |
| tsq | Transact-SQL Script |
| tsql | Transact-SQL Script |
| tt | Visual Studio T4 Text Template |
| ttcn | TTCN-3 Script |
| tte | TextTransformer Interpreter |
| tti | TextTransformer Script |
| ttinclude | Visual Studio T4 Text Template Include |
| ttr | TextTransformer Productions |
| ttt | TextTransformer Tests |
| ttw | IBM Rational Tau Workspace |
| ttx | TextTransformer Tokens |
| tu | Turing Unit File |
| tui | NI LabWindows User Interface Data |
| tuneao | Aleph One Data |
| tup | Tup Data |
| tur | Turing Source Code |
| tvsconfig | RAD Studio Modeling Configuration |
| twig | Twig Template |
| txg | Toad Data Modeler Package |
| txl | TXL Source Code |
| txs | Tiny XML Server Script |
| tyb | Ty-Basic Source Code |
| tzjs | Turbulenz Java Application |
| tzo | Turbulenz Object |