| tcs | Tahoe Server Content Source |
| tcsh | TCSH Shell Script |
| tcv | SD Test Coverage Vector File |
| tcz | TDF Czar Script |
| td2 | Turbo Debugger for Win32 Configuration Data |
| tdb | ProWorx NXT Title Data with Blocking |
| tdbd | TurboDB Database |
| tdf | ProWorx NXT Title Data File |
| tdk | Borland Turbo Debugger Keystroke Recording Data |
| tdl | MathType Translator Definition Language |
| tdlog | Microsoft Visual Studio IntelliTrace Log |
| tdm | LabVIEW Binary Measurement with XML Header |
| tdms | LabVIEW TDM Streaming Data |
| tds | Turbo Debugger Symbols |
| tdw | Turbo Debugger for Windows Data |
| tdx | LabVIEW Binary Measurement Data |
| tdy | Today BuildProfessional Application Data |
| tem | Microsoft Frontpage Website Template |
| tes | Tool Encapsulation Specification |
| testsettings | Visual Studio Test Settings Data |
| texture | Diesel Engine Texture Data |
| tf | Xilinx ISE Verilog Test Bench |
| tfp | ProWorx NXT Full Page Data File |
| tfs | Borland Turbo Profiler Statistical Data |
| tgl | IBM MDWorkbench Text Generation Language Script |
| 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 |