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