| bkup | Groundspeak Wherigo Backup File |
| bky | SmartWare Backup Keyboard Data |
| bkz | FileFort Backup Data |
| bla | Blaise Datamodel |
| blb | Act! Blob Data |
| blb | Treepad Database Blob Data |
| bldinp | OnScale Build Input Data |
| blend1 | Blender Document Backup |
| blend2 | Blender Document Backup |
| blf | CLFS BaseLog |
| blf | MasterWorks Data |
| blif | Berkeley Logic Interchange Format Data |
| blk | Lightscape Block File |
| bll | ENVI Bad Lines List |
| blm | Rightmove Bulk Load Mass Data |
| bln | Golden Software Blanking |
| blo | IBM DB2 Binary Large Object Data |
| blob | IBM DB2 Binary Large Object Data |
| blob | Valve Steam Client Registry Data |
| blockplt | Lego Mindstorms NXT Block Palette Data |
| blr | Biacore BIAlite Project Data |
| blrb | Apple Extensions Manager Info Data |
| blt | AOL Instant Messenger Buddy List File |
| bluebutton | VA Blue Button Data |
| bluestacks | BlueStacks App Player Data |
| blwd | Claris Home Page Data |
| blx | Magellan Mapsend Map Data |
| bm2 | Boardmaker Board |
| bm3 | Sony Ericsson PC Suite Backup |
| bmap | Block Map File |
| bmb | Onyx BAMBOO Modeler Data |
| bmd5 | BookmarkingDaemon Data |
| bmdx | eXtendable Wad Editor BMDX Data |
| bmi | Blaise Metafile |
| bmk | WindLDR Bookmarks File |
