| tdw | Turbo Debugger for Windows Data |
| tdx | LabVIEW Binary Measurement Data |
| tem | Microsoft Frontpage Website Template |
| tes | Tool Encapsulation Specification |
| testrunconfig | Visual Studio Test Run Configuration |
| testsettings | Visual Studio Test Settings |
| textfactory | BBEdit Text Factory |
| tf | Xilinx ISE Verilog Test Bench |
| tfp | ProWorx NXT Full Page Data File |
| tfs | Borland Turbo Profiler Statistical Data |
| tgn | LaTeX Table Generator Data |
| tgr | Apex Trigger File |
| tgt | Watcom IDE Target File |
| thm | ForeUI Theme Data |
| thor | Thor Source Code |
| ti | Turing Include File |
| tiprogram | TI-BASIC Program |
| tk | Tk Script |
| tkm | tkMOO-light Script |
| tkn | Liberty BASIC Tokenized Source |
| tlb | Visual Basic OLE Type Library |
| tld | Tag Library Descriptor |
| tlh | Visual C++ TLH Header |
| tli | Visual C++ TLI Header |
| tmac | Troff Macros File |
| tmc | Windows Trace Message Control File |
| tmf | Windows Trace Message Format File |
| tmf | Trace Message Format File |
| tmh | Windows Trace Message Header File |
| tmk | Turbo Pascal Tour Data |
