File extensions start with character 'Y'
| File Type | Category | File Format | |
|---|---|---|---|
| .y4m | Digital Video Files | YUV4MPEG2 Video File | |
| .yam | Data Files | Yahoo! Auctions Data | |
| .ychat | Data Files | Yahoo! Messenger Chat Log | |
| .ygf | Data Files | Y Graph Format File | |
| .yml | Development Files | YAML Document |