| Extension | Description | File Type |
|---|
| b | Basic language source file | Developer Files |
| b00 | CD Image Segment File. | Disk Image Files |
| b5i | Blindwrite 5 Disk Image File | Disk Image Files |
| b5t | Blindwrite 5 Image Information File | Disk Image Files |
| b6i | Blindwrite Image File | Disk Image Files |
| b6t | Blindwrite 6 Image Information File | Disk Image Files |
| backup | Ad-Aware Reference File | Misc Files |
| bak | Backup File | Backup Files |
| bas | BASIC Source Code File | Developer Files |
| bat | Batch File | Executable Files |
| bba | Settler IV Archive File | Archived Files |
| bbb | Blackberry Backup File | Backup Files |
| bblx | E-Sword Module File | Misc Files |
| bc! | Bitcomet Incompleted Download File | Misc Files |
| bcf | Belarc Advisor Content File | Misc Files |
| bcr | Map & Guide Station File | Misc Files |
| bdm | AVCHD Index File | Video Files |
| bdmv | Blu-ray information file | Video Files |
| bfg | CQuickTrans File | Misc Files |
| bfs | Tivoli Storage Manager File | Data Files |
| bgl | Babylon Glossary File | Misc Files |
| bh | BlackHole Compressed File | Archived Files |
| bibtex | BibTeX document | Text Files |
| bif | Bioware Resource File | Game Files |
| big | Electronic Arts Data File | Game Files |
| bik | Bink Video Codec File | Video Files |
| bikey | Bohemia Interactive Key File | Game Files |
| bin | Cuesheet CD/DVD Image | Disk Image Files |
| bk | FrameMaker Book File | Document Files |
| bk | Backup File | Misc Files |
| bkf | Windows Backup File | Backup Files |
| bkp | Backup File | Backup Files |
| blend | Blender 3D File | 3D Files |
| blf | Bantec Scanner Driver File | Misc Files |
| blf | Windows Registry Recovery File | System Files |
| blg | Binary Performance Log File | Data Files |
| blob | Steam Archive File | Game Files |
| bmf | Floor Plan 3D Project File | 3D Files |
| bmk | Windows Help Bookmark File | Text Files |
| bmp | BMP File Format | Graphic Files |
| bndl | Bundle File | System Files |
| bnk | AdLib Instrument Bank File | Audio Files |
| bnp | Sony Video Data File | Video Files |
| bok | Prostores Dynamic Web Page File | Layout Files |
| boot | Installshield File | Misc Files |
| box | Mailbox File | Misc Files |
| bpl | Borland Package Library File | Developer Files |
| brd | EAGLE Circuit Board Layout File | CAD Files |
| brstm | BRSTM File | Audio Files |
| bsa | Bethseda Softworks Archive File | Game Files |
| bsp | Quake Map File | Game Files |
| bsv | Bluespec System Verilog File | Developer Files |
| bt! | BitTorrent Partial Download File | Misc Files |
| btn | Buttonware File | Data Files |
| bun | Monkey Island 3 Game Archive File | Game Files |
| bun | Bundled Audio Files | Audio Files |
| bup | DVD File Backup | Backup Files |
| bwa | BlindWrite Disk Image Information File | 3D Files |
| bwi | Blindwrite Disk Image File | Disk Image Files |
| bws | Blindwrite Sub Channel Data File | Disk Image Files |
| bwt | Blindwrite Image File | Disk Image Files |
| bz2 | Bzip2 Compressed File | Archived Files |