| xtea | XTEA Encyrpted Data |
| xtra | Adobe Director Xtra Extension |
| xuv | BlueFlash Firmware Image |
| xxc | Centraline COACH Controller Firmware |
| xxe_addon | XMLmind XML Editor Add-on |
| ybd | YobiDrive Link |
| yenc | yEnc Encoded File |
| ymp | YaST Meta Package |
| ync | yEnc Encoded File |
| yps | Yahoo! Messenger Data |
| yti | Google Picasa Plugin |
| yxwz | Alteryx Designer Analytic App |
| z1 | ZoneAlarm Renamed VB |
| zfsendto | Windows Compressed Folder Shortcut |
| zg | Honeywell MP Compact4 Firmware |
| zgi | Zoomerang Web Survey Page |
| zgk | ZIPGenius Key Data |
| zipenx | Egis Encrypted Data |
| zl0 | ZoneAlarm MailSafe Renamed ADE File |
| zl3 | ZoneAlarm MailSafe Renamed BAT File |
| zl4 | ZoneAlarm MailSafe Renamed CHM File |
| zl8 | ZoneAlarm MailSafe Renamed CRT File |
| zl9 | ZoneAlarm MailSafe Renamed EXE |
| zld | ZoneAlarm MailSafe Renamed INS File |
| zlf | ZoneAlarm MailSafe Renamed JSE File |
| zlh | ZoneAlarm MailSafe Renamed MDB File |
| zli | ZoneAlarm MailSafe Renamed MDE File |
| zlj | ZoneAlarm MailSafe Renamed MSC File |
| zlk | ZoneAlarm MailSafe Renamed MSI File |
| zll | ZoneAlarm MailSafe Renamed MSP File |
