| .BAC | Avantrix Inc. | Varmuuskopiointitiedostot | Backup Plus Backup File | Backup Plus | Avantrix Inc. |
| .BACKUP | Google | Varmuuskopiointitiedostot | Google Android Backup File | Google Android | Google |
| .BACKUP DEFINITION FILE | Willowsoft Creek Software | Varmuuskopiointitiedostot | Backup Definition File | Backup Made Simple | Willowsoft Creek Software |
| .BAK | Various Developers | Varmuuskopiointitiedostot | General Backup File | Microsoft SQL Server | Microsoft Corporation |
| .BAZ | Unknown Developer | Varmuuskopiointitiedostot | Acomba Accounting Suite Backup | Acomba Accounting Suite | ACCEO |
| .BBB | Reincubate | Varmuuskopiointitiedostot | BlackBerry Mobile Phone Backup File | Research In Motion BlackBerry Desktop Manager | BlackBerry |
| .BBK | Freebyte | Varmuuskopiointitiedostot | TreePad Backup File | Treepad | Freebyte |
| .BBZ | BitBlaze | Varmuuskopiointitiedostot | Bitblaze Audio File | Unknown Software | Unknown Developer |
| .BCA | Nemetschek Group | Varmuuskopiointitiedostot | Allplan Backup Catalog File | Allplan Engineering | Nemetschek Group |
| .BCK | Hewlett-Packard | Varmuuskopiointitiedostot | VMX Backup File | OpenVMS | Hewlett-Packard |
| .BCKP | Lavasoft | Varmuuskopiointitiedostot | Ad-Aware Quarantined File | Ad-Aware | Lavasoft |
| .BCM | Adobe Systems Incorporated | Varmuuskopiointitiedostot | Adobe Bridge Cache File | Adobe Bridge CC | Adobe Systems Incorporated |
| .BDB | Microsoft Corporation | Varmuuskopiointitiedostot | Microsoft Works Database Backup File | Microsoft Access | Microsoft Corporation |
| .BDF | Willowsoft Creek Software | Varmuuskopiointitiedostot | Backup Definition File | Backup Made Simple | Willowsoft Creek Software |
| .BEE | Andrew Filinsky | Varmuuskopiointitiedostot | Bee Archiver Compressed Archive File | BeeGui Bee Archiver | Andrew Filinsky |
| .BFF | IBM | Varmuuskopiointitiedostot | Backup File Format | AIX Toolbox | IBM |
| .BFW | SmartWare Corporation | Varmuuskopiointitiedostot | SmartWare Backup Cross-tab Definition | SmartWare | SmartWare Corporation |
| .BIF | MagicISO Inc. | Varmuuskopiointitiedostot | Boot Information File | MagicISO | MagicISO Inc. |
| .BJF | NTI Corporation | Varmuuskopiointitiedostot | NTI Backup Now Backup Job File | NTI Backup Now | NTI Corporation |
| .BK! | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BK1 | Autodesk, Inc. | Varmuuskopiointitiedostot | Autodesk Backup File | Autodesk AutoCAD Ecscad | Autodesk, Inc. |
| .BK3 | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BK4 | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BK6 | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BK8 | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BK9 | Corel | Varmuuskopiointitiedostot | Corel WordPerfect Document Backup File | Corel WordPerfect | Corel |
| .BKC | Softland | Varmuuskopiointitiedostot | Backup4all Backup Catalog | Backup4all | Softland |
| .BKF | Microsoft Corporation | Varmuuskopiointitiedostot | Windows Backup Utility File | Microsoft Windows NT Backup - Restore Utility | Microsoft Corporation |
| .BKP | Various Developers | Varmuuskopiointitiedostot | Backup File | Zapback | Zaplots Games, Inc. |
| .BKU | Sage | Varmuuskopiointitiedostot | Timeslips Backup | Timeslips | Sage |
| .BKUP | cPanel | Varmuuskopiointitiedostot | Generic Backup File | cPanel and WebHost Manager | cPanel |
| .BKY | SmartWare Corporation | Varmuuskopiointitiedostot | SmartWare Backup Keyboard File | SmartWare | SmartWare Corporation |
| .BKZ | NCH Software | Varmuuskopiointitiedostot | FileFort Backup File | NCH FileFort | NCH Software |
| .BMK | return7, LLC | Varmuuskopiointitiedostot | BillMinder Backup File | return7 BillMinder | return7, LLC |
| .BPA | SimpleTech | Varmuuskopiointitiedostot | StorageSync Backup Archive | StorageSync | SimpleTech |
| .BPN | Graphisoft | Varmuuskopiointitiedostot | ArchiCAD Project Backup File | ARCHICAD | Graphisoft |
| .BPP | SoftVelocity | Varmuuskopiointitiedostot | Clarion Backup Application | Clarion | SoftVelocity |
| .BPS | Symantec Corporation | Varmuuskopiointitiedostot | BPS Programs Virus File | Kaspersky Anti-Virus | Kaspersky Lab |
| .BQY | Oracle Corporation | Varmuuskopiointitiedostot | Brio Query File | Internet Explorer | Microsoft Corporation |
| .BTX | SmartWare Corporation | Varmuuskopiointitiedostot | SmartWare Backup Text File | SmartWare | SmartWare Corporation |
| .BUC | Adobe Systems Incorporated | Varmuuskopiointitiedostot | Adobe Photoshop Elements Backup File | Adobe Photoshop Elements | Adobe Systems Incorporated |
| .BUP | Various Developers | Varmuuskopiointitiedostot | Backup File | Zapback | Zaplots Games, Inc. |
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