File Extension Library

.BAK File Extension

  • Developer by: Mozilla
  • Category: Backup Files

What is an .BAK file?

.BAK file extension is created by Mozilla. .BAK has been classified as Backup Files.

.BAK is Firefox Bookmarks Backup

A BAK file is a backup of the Firefox bookmarks file, which can be used to replace saved bookmarks in case the main bookmarks file becomes corrupted. It is automatically generated by the Firefox web browser and typically named "bookmarks.bak".

The bookmarks.bak file is located in the following directories on Windows and Macintosh systems:

  • Windows -
    C:\Documents and Settings\UserName\Application Data\MozillaFirefox\Profiles\[random-name]
  • Mac -
    /Users/[username]/Library/Application Support/Firefox/Profiles/[random-name].default
List of all softwares that can open the Firefox Bookmarks Backup
Mozilla Firefox
Mozilla Firefox
File Type 2 Backup File
Category: Backup Files Format: Text and Binary

A BAK file is a backup of another document or file, commonly created automatically by software programs or by the operating system. The file most often just contains a copy of the original file and can be restored to the original by replacing the ".bak" extension with the original extension.

Often BAK files are created by simply appending ".bak" to the original filename. For example, document.doc may have a backup file document.doc.bak.

NOTE: An example program that uses the ".bak" extension is AutoCAD. Windows may also create BAK files for the System.ini and Win.ini files.

List of all softwares that can open the Backup File
Autodesk AutoCAD 2018
Microsoft SQL Server 2016
File Type 3 ACT! Backup File
Developer by: The Sage Group Category: Backup Files Format: Binary

Backup file created by ACT!, an application used for customer relationship management (CRM); contains a backup of CRM data, which includes customer information such as names, address information, and history.

ACT! BAK files are used for restoring data in the event the CRM data is lost. They are usually created on a periodic basis and when upgrading ACT! software.

NOTE: Sage ACT! became Swiftpage Act! in 2013.

List of all softwares that can open the ACT! Backup File
Swiftpage Act!
File Type 4 MobileTrans Backup File
Developer by: Wondershare Category: Backup Files

A BAK file is a backup file created by Wondershare MobileTrans, a program used to backup and transfer data from and to devices. It contains data backed up from a device, such as contacts, messages, calendar information, call logs, photos, music, videos, apps, and app data.

BAK files are the primary file type associated with MobileTrans. The file is created when backing up a phone to a computer. To do this in MobileTrans, click "Back Up Your Phone" on the homepage of the program, select the content to backup, and click "Start Transfer". The BAK file will then be created to store the backup data and placed in the following directory:


To restore a BAK file to a device in MobileTrans, click "Restore From Backups" on the homepage of the program, click "MobileTrans", select the BAK file you want to restore, and click "Start Transfer".

Common BAK Filenames

[name of device]_[date]_[time].bak - Naming convention for BAK files created by MobileTrans.

List of all softwares that can open the MobileTrans Backup File
Wondershare MobileTrans
Wondershare MobileTrans
File Type 5 Finale Backup File
Developer by: MakeMusic Category: Backup Files

File created by Finale, a music notation application for playing instruments, vocals, etc.; replaced by the .BAKX file, which was released in Finale 2014; contains backup data for .MUS files; created when MUS files are saved by the user.

To create a BAK file:

  • You must first enable the backup creation option.
  • Select Finale [version] → Preferences....
  • Select "Save and Print" in the list on the left of the "Preferences" window, check the "Make Backups When Saving Files" checkbox, and click OK.
  • Now when you save your MUS file, a BAK file will be created.
  • List of all softwares that can open the Finale Backup File
    MakeMusic Finale
    MakeMusic Finale

    How to Open .BAK file on different platforms

    Open .BAK File on Windows

    • Right-click a .BAK
    • Left-click "Open With" > "Choose another app"
    • Select the program that opens .BAK file and Select check box "Always use this app to open .BAK files" Press "Ok"

    Open .BAK File on Mac

    • Right-click (or Ctrl + Left-click) the .BAK file
    • Click "Open With" > "Other.."
    • Then choose another program from the app list and press "Open"
    • Select check box "Turn on" for "Always open in app"

    Open .BAK File on Linux

    Right click on the .BAK file, choose "Open with" and select a program from the list above

    Open .BAK File on iPhone

    Select a file. If you don't see an application to open the .BAK file, tap "Share" and choose the right app.
    Method 2
    Save the file. Then open the app «Files». Touch and hold the file, then release your finger. You will see a black menu bar. After that tap "Share" and select an application.

    Open .BAK File on Android

    Tap the Settings icon on an Android smartphone, then select «Applications». Click the Settings icon in the upper right corner of the screen, to change the default apps.
    If you want to open, edit, save or even convert .BAK files on Android, then your best bet is to download one of the dedicated apps available on Google Play.

    How to fix problems with .BAK files

    1. You need to update the application that you normally use to open .BAK files. Only the latest version of the software supports the current .BAK file format
    2. You need to check the .BAK file for viruses. To do this, you need to scan it with a popular antivirus (Norton, Nod32, Kaspersky, Dr.Web, etc.)