| to4 | Top 4 Compressed Data |
| toppkg | TopSolid Package |
| tpafz | YouMinds Composer Portable Archive |
| tpk | Tizen Application Package |
| tpkg | tpkg-builder data |
| tpxz | Pixz Compressed Tarball |
| ts3_iconpack | TeamSpeak 3 Icon Package |
| tsep | Tekla Structures Extension Package |
| ttpkg | TomTom Package |
| txz | XZ Compressed Tar Archive |
| tz | Compressed Tape Archive |
| tzb | TAR.Z.btoa Compressed Archive |
| tzip | Tzip Compressed Text |
| tzp | TrueZIP Ecnrypted JAR Archive |
| tzr | ANSYS IcePak Project Package |
| uar | Uniface Deployment Archive |
| uas | PhotoImpact Backup Archive |
| uc2 | UltraCompressor 2 Compressed Archive |
| ucas | Unreal Engine 4 Archive |
| uea | Protector Suite QL Encrypted Archive |
| ueed | Uconomix Encryption Engine Encrypted Directory |
| uexp | UE Viewer Package |
| ufa | UFA Compressed Archive |
| uha | UHarc Archive |
| uharc | UHarc Archive |
| upx | UPX Compressed File |
| ustar | Tape Archive |
| utoc | Unreal Engine 4 Archive Metadata |
| uws | UniTrader 2006 Website Archive |
| uwt | UniTrader Website Template Archive |
