| Extension | File Type | Files scanned | Contributor |
| Y3D | YACE64 3D layout | 4 | |
| Y4M | YUV4MPEG2 video | 4 | |
| YAA | YAA compressed archive | 3 | |
| YACE | YACE64 saved state | 6 | |
| YAFA | YAFA Animation | 15 | |
| YAL | Arts and Letters clip art library | 25 | |
| YAML | AppleWin Saved State (v2) | 7 | |
| YAML | AppleWin controller configuration | 12 | |
| YAML | FactoryTalk Optix project UI design | 8 | |
| YAML | Snapcraft build info | 15 | |
| YAML | Snapcraft build info (with rem) | 5 | |
| YAML/YML | YAML serialized data | 37 | |
| YAML/YML | YAML serialized data (UTF-8) | 19 | |
| YANG | YANG data model | 18 | |
| YAY0 | Nintendo Yay0 compressed data | 2 | |
| YBK | YanCEyWare Reader eBook | 12 | |
| YBN/YDD/YDR/YFT/YMAP/YMT/YTYP | Grand Theft Auto 5 game data (generic) | 122 | |
| YBS | YBS compressed archive | 3 | |
| YC | YAC compressed archive | 3 | |
| YDL | SGI YAODL 3d vector data | 3 | |
| YDR | YouiDraw Drawing | 4 | |
| YES | Quick Bible document | 8 | |
| YFS | YSFlight mission | 26 | |
| YGR | Yu-Gi-Oh Tag Force game data archive | 2 | |
| YKA | Yenka model | 21 | |
| YM | ST-Sound YM chiptune (generic) | 18 | |
| YM | ST-Sound YM chiptune (v6) | 13 | |
| YM/YMST | YM2149 song | 334 | |
| YMD | Yach*PMS module | 6 | |
| YMF | YMF sample | 2 | |
| YMF | YMF song/music | 3 | |
| YML | Espanso Package | 8 | |
| YML | Espanso Package (with rem) | 8 | |
| YMP | YaST MetaPackage | 10 | |
| YMV | Yabause movie capture | 4 | |
| YNC | yEnc Encoded | 26 | |
| YOBJ | Yukes 3D Object | 4 | |
| YOG | Yog video | 2 | |
| YOP | Psygnosis YOP video | 3 | |
| YP | Young Picasso bitmap | 3 | |
| YPC | WhyPic bitmap | 2 | |
| YPR | BYOB project | 11 | |
| YRA | TrainController Animation | 47 | |
| YRP | YGOPRO replay | 5 | |
| YRR | TrainController Railroad | 14 | |
| YSP | BYOB sprite | 43 | |
| YTD | Grand Theft Auto 5 Texture Dictionary | 23 | |
| YTF | Picasa font cache | 31 | |
| YTR | IRIS OCR data | 6 | |
| YTT | YouTube Timed Text subtitles | 4 | |
| YUVN/IFF | IFF YUVN bitmap | 3 | |
| YY | GNU Bison grammar | 14 | |
| YY | GNU Bison grammar (with rem) | 14 | |
| YYP | GameMaker Studio Project | 38 | |
| YYY | CrLZH compressed | 11 | Erik Siers |
| YYZ | Zipped GameMaker project | 17 | |
| YZ1 | Yamazaki Zipper compressed archive | 5 | |
