The File Extensions Database


.999 File Extension

  • Developer by: The Sage Group plc
  • Category: Backup Files

What is an .999 file?

.999 is Sage backup

The 999 file extension is or was used by some Sage applications for their backup files. This type of backup was used on the old Sega games and there is no more information about this file.


How to open:

Use Sage programs to work with *.999 files.

How to convert:

As far as we know, this .999 file type can't be converted to any other file format. This is usually the case of system, configuration, temporary, or data files containing data exclusive to only one software and used for its own purposes. Also some proprietary or closed file formats cannot be converted to more common file types in order to protect the intellectual property of the developer, which is for example the case of some DRM-protected multimedia files.

How to solve problems with 999 files

  • Associate the 999 file extension with the correct application. On :
    Windows: Right click on any 999 file and then click "Open with" > "Choose another app". Now select another program and check the box "Always use this app to open *.999 files". Mac: Right click (or Ctrl-click) the 999 file, then click "Open with" > "Other...". Then choose another program and check the "Always Open With" box. Linux: Right click on the file, and select "Open with" and choose another program. iPhone: Tap the file. If you do not see an app to open the file, then tap Share "Share" and choose an app. Alternatively, save the file. Then open the Files app Files app. There long-press on the file, then release your finger. You will see a black menu bar. Then tap "Share" and select an app. Android: Tap the Settings icon on your smartphone, then tap on the Apps section. There tap the Options icon in the top right-hand corner of the screen to change the default apps.
  • Update your software that should actually open .999 is Sage backup. Because only the current version supports the latest 999 file format. Search, therefore, e.g. on the The Sage Group plc manufacturer website after an available .999 is Sage backup update.
  • To make sure that your 999 file is not corrupted or virus-infected, get the file again and scan it with antivirus software.