| thor | Thor Source Code |
| ti | Turing Include File |
| tio | Crestron SIMPL Model Definitions Data |
| 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 | Trace Message Format File |
| tmf | Windows Trace Message Format File |
| tmh | Windows Trace Message Header File |
| tmk | Turbo Pascal Tour Data |
| tml | Tapestry Markup Language Document |
| tmml | Tcl Manual Markup Language File |
| tmpl | BlueJ Template File |
| tmx | Translation Memory Exchange Document |
| tnm | Synopsys Synplify Time Names Data |
| tok | Borland C++ External Tokens File |
| tom | Tom Source Code |
| tombstone | Android System Tombstone Data |
| toml | TOML Source Code |
| tools | DJGPP Tools Data |
| tox | TouchDesigner Component Data |
| tp1 | SPLat Active Template |
| tph | Turbo Pascal Help |
