| .USTAR | Smith Micro Software | Data Files | Uniform Standard Tape Archive Format File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .UU | Open Source | Encoded Files | Uuencoded File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .UUE | Open Source | Encoded Files | Uuencoded File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .WAR | Oracle Corporation | Compressed Files | Java Web Archive | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .WMZ | Microsoft Corporation | Settings Files | Compressed Windows Media Player Skin | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Y | Microsoft Corporation | Raster Image Files | Subsampled Raw YUV Image | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .YENC | Open Source | Encoded Files | yEnc File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .YNC | Open Source | Encoded Files | yEnc Encoded File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z | Smith Micro Software | Compressed Files | Unix Compressed File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z01 | Corel | Compressed Files | WinZip First Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z02 | Corel | Compressed Files | WinZip Second Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z03 | Corel | Compressed Files | WinZip Third Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z04 | Corel | Compressed Files | WinZip Fourth Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z05 | Corel | Compressed Files | WinZip Fifth Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z06 | Corel | Compressed Files | WinZip Sixth Split Zip File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z07 | Eugene Roshal | Compressed Files | Split Multi-volume RAR Compressed File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z08 | Eugene Roshal | Compressed Files | Split Multi-volume RAR Compressed File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z09 | Eugene Roshal | Compressed Files | Split Multi-volume RAR Compressed File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .Z96 | Eugene Roshal | Compressed Files | Split Multi-volume RAR Compressed File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .ZIP | Winrar | Compressed Files | Zipped File | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .ZIP2 | Smith Micro Software | Compressed Files | StuffIt Archive | Smith Micro StuffIt Deluxe | Smith Micro Software |
| .ZPI | Winrar | Compressed Files | Zipped File | Smith Micro StuffIt Deluxe | Smith Micro Software |
of 2 
