В алфавитном порядке: Y

Расширение файла	Описание файла	Создатель/производитель
.y	Yacc Source File	Stephen C. Johnson
.y3a	Yu-Gi-Oh! ONLINE 3 Avatar File	Konami
.y3d	Yu-Gi-Oh! ONLINE 3 Deck File	Konami
.y4m	YUV4MPEG2 Video File	N/A
.yab	Yabasic Source Code	Yabasic
.yal	Arts & Letters Clipart Library	Arts and Letters
.yam	Yahoo! Auctions Data	Yahoo!
.yaml	YAML Document	N/A
.yaodl	PowerFlip 3D Image File	Silicon Graphics
.ybd	YobiDrive Link File	EZC Group
.ybk	YanCEyWare eBook	YanCEyWare
.ychat	Yahoo! Messenger Chat Log	Yahoo!
.ycm	Yugioh Card Maker File	Super Simple Games
.ydc	Yu-Gi-Oh! Card Deck File	Konami
.ydl	PowerFlip YAODL 3D Image File	Silicon Graphics
.ydr	Yu-Gi-Oh! Power of Chaos Replay File	Konami
.ydt	Yu-Gi-Oh! Power of Chaos Data File	Konami
.yenc	yEnc File	N/A
.yfs	YSFLIGHT Mission File	YSFLIGHT.com
.ygf	Y Graph Format File	yWorks
.yka	Yenka Model File	Crocodile Clips
.ym	Atari ST Audio File	Atari
.ymg	Yahoo! Messenger File	Yahoo!
.yml	YAML Document	N/A
.yml2	YML Script	N/A
.ymp	YaST Metapackage File	YaST
.ync	yEnc Encoded File	N/A
.yog	Outerra Captured Video File	Outerra
.yookoo	Yookoo Player Playlist File	Penguin George
.ypr	BYOB Project File	BYOB
.yps	Yahoo! Messenger Data File	Yahoo!
.ysp	BYOB Sprite File	BYOB
.ytf	Google Picasa Font Cache	Google
.yuv	YUV Encoded Image File	N/A
.yz	YAC Compressed File	YAC
.yz1	Yamazaki ZIPPER File	Yamazaki ZIPPER