| .WPP | Serif | Ficheiros de Áudio | WebPlus Project File | Serif WebPlus | Serif |
| .WRK | Cakewalk, Inc. | Ficheiros de Áudio | Cakewalk Music Project | Cakewalk SONAR | Cakewalk, Inc. |
| .WSQ | UTAU Team | Ficheiros de Áudio | UTAU File | UTAU | Vocal Synthesizer |
| .WUS | WUSSOFT | Ficheiros de Áudio | WUTG Tagged Audio File | WUSSoft AutoSound | WUSSOFT |
| .WUT | WUSSOFT | Ficheiros de Áudio | WUTG Tag File | WUTG Editor | WUSSOFT |
| .WV | David Bryant | Ficheiros de Áudio | WavPack Audio File | Nullsoft Winamp | Nullsoft |
| .WVC | Open Source | Ficheiros de Áudio | WavPack Correction File | WavPack | Open Source |
| .WVE | Wondershare Software Co., Ltd. | Ficheiros de Áudio | Wondershare Filmora Project File | Wondershare Filmora | Wondershare Software Co., Ltd. |
| .X3V | Yamaha Corporation | Ficheiros de Áudio | Yamaha Motif Audio | Translator Professional | Chicken Systems |
| .XA | Electronic Arts | Ficheiros de Áudio | The Sims Audio File | Electronic Arts SimCity 4 | Electronic Arts |
| .XAD | Riven the Mage | Ficheiros de Áudio | eXotic ADlib Sound Format File | Unknown Software | Unknown Developer |
| .XFS | Elabtronics Company | Ficheiros de Áudio | eRacer Sound File | CoreChart | Elabtronics Company |
| .XI | Starbreeze Studios | Ficheiros de Áudio | Fasttracker 2 Extended Instrument File | Awave Studio | FMJ-Software |
| .XKR | Sing-Magic | Ficheiros de Áudio | Sing Magic Karaoke Song | Sing-Magic Karaoke | Sing-Magic |
| .XM | Starbreeze Studios | Ficheiros de Áudio | FastTracker 2 Extended Module | ModPlug Player | Open Source |
| .XMF | Open Source | Ficheiros de Áudio | Cal3D XML Mesh File | Cal3DViewer | Open Source |
| .XMI | Object Management Group (OMG) | Ficheiros de Áudio | XML Metadata Interchange File | Eclipse IDE for Java Developers | The Eclipse Foundation |
| .XMS | Alexander Gross | Ficheiros de Áudio | Music Studio Project | Alexander Gross Music Studio | Alexander Gross |
| .XMZ | Starbreeze Studios | Ficheiros de Áudio | FastTracker 2 Extended Module | ModPlug Player | Open Source |
| .XP | Starbreeze Studios | Ficheiros de Áudio | Fastracker 2 Pattern | Fasttracker | Starbreeze Studios |
| .XPA | SoniqCast, LLC | Ficheiros de Áudio | SoniqSync Extended Playlist | SoniqSync | SoniqCast, LLC |
| .XPF | Open Source | Ficheiros de Áudio | Linux MultiMedia Studio Preset File | LMMS | Open Source |
| .XPL | Interscape | Ficheiros de Áudio | LcdStudio Playlist File | LCDStudio | Interscape |
| .XRNS | Renoise.com | Ficheiros de Áudio | Renoise Song File | Renoise | Renoise.com |
| .XSB | Microsoft Corporation | Ficheiros de Áudio | XACT Sound Bank | Microsoft XACT | Microsoft Corporation |
| .XSP | Open Source | Ficheiros de Áudio | Kodi Smart Playlist File | Kodi | Open Source |
| .XSPF | VideoLAN | Ficheiros de Áudio | XSPF Playlist File | VLC Media Player | VideoLAN |
| .XT | Derick Rethans | Ficheiros de Áudio | Xdebug Trace File | Xdebug | Derick Rethans |
| .XWB | Microsoft Corporation | Ficheiros de Áudio | XACT Wave Bank | Microsoft XACT | Microsoft Corporation |
| .XWC | Starbreeze Studios | Ficheiros de Áudio | Starbreeze Sound Data | Knights of the Temple | Starbreeze Studios |
| .XWV | Valve | Ficheiros de Áudio | Valve Xbox360 Audio Data | Valve Source SDK | Valve |
| .YGD | Open Source | Ficheiros de Áudio | YouGooDai Playlist File | YouGooDai | Open Source |
| .YM | Atari Corporation | Ficheiros de Áudio | Atari ST Audio File | Nullsoft Winamp | Nullsoft |
| .YNX | Unknown Developer | Ficheiros de Áudio | Segmax Seqprest Compressed File | Unknown Software | Unknown Developer |
| .Z00 | Casio Computer Co., Ltd. | Ficheiros de Áudio | Casio WK-3000 Rythm Data | Casio Data Manager | Casio Computer Co., Ltd. |
| .ZAB | VideoLAN | Ficheiros de Áudio | Zipped Audio Book | VLC Media Player | VideoLAN |
| .ZAF | Zoom Corporation | Ficheiros de Áudio | Zoom Audio Data | Zoom Player | Inmatrix Media Solutions |
| .ZAX | Zaxcom | Ficheiros de Áudio | Zaxcom Audio Data | Unknown Software | Unknown Developer |
| .ZEL | Andrew Maclean | Ficheiros de Áudio | Zel MIDI Source File | Zel | Andrew Maclean |
| .ZPA | zplane.development GmbH & Co. KG | Ficheiros de Áudio | Vielklang Audio Metadata File | Steinberg Cubase | Steinberg |
| .ZPL | Inmatrix Media Solutions | Ficheiros de Áudio | Zoom Player Play List | Zoom Player | Inmatrix Media Solutions |
| .ZVD | Zyxel Communications | Ficheiros de Áudio | ZyXEL Voice File | Zyxel Z-Fax modem Software | Zyxel Communications |
| .ZVR | SAFA Inc. | Ficheiros de Áudio | SAFA Media Audio File | Microsoft Windows Media Player | Microsoft Corporation |
| .ZYX | Zyxel Communications | Ficheiros de Áudio | ZyXEL Voice File | Zyxel Z-Fax modem Software | Zyxel Communications |
| ._1 | Interscape | Ficheiros de Áudio | Tuningwrench Audio Utility Compressed Audio | Tuningwrench | Interscape |
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