| totalslayout | Totals Invoice Layout File |
| tow | TOWER Model |
| tp3 | Harvard Graphics 3.0 Template |
| tpd | Treepad v7 Database |
| tpl | ArchiCAD Project Template |
| tpl | DataCAD Template Document |
| tpt | ThumbsPlus Template |
| tpt | Treepad Template |
| tpz | Treepad Zipped Database |
| tracwiki | Eclipse IDE WikiText Document |
| trelby | Trelby Document |
| tsb | 3dMD 3D Image |
| tse | Light Map Maker Scene |
| tst | Corel WordPerfect 5 Printer Test Document |
| tst | ExamView Test File |
| tsv | Tab-Separated Values |
| ttax | Newton Dictate Transcription Document |
| ttl | Turtle Language Document |
| ttml | Timed Text Markup Language Document |
| tts | ToolBook Translation System Document |
| tvj | TrueView Job Ticket |
| twd | MindMapper Map |
| twdi | ThinkWise Document |
| twds | MindMapper Single File |
| twdx | MindMapper 12 XML Map |
| twiki | Eclipse IDE WikiText Document |
| txd | RenderWare Texture Data |
| txe | Enriched Text File |
| txh | Lightweight Markup Language Text |
| txlf | SDL Trados XLIFF Document |
| txml | Wordfast TXML Document |
| txt | Plain Text Document |
| u3d | Universal 3D File |
| ubz | Open-Sankore Document |
| ucls | ObjectAid UML Explorer Class Diagram |