How to open OST files

Did your computer fail to open an OST file? We explain what OST files are and recommend software that we know can open or convert your files.

What is an OST file?

OST files are Outlook Exchange Offline Storage files, which you can read more about below.

The OST file extension indicates to your device which app can open the file. However, different apps may use the same file extension for different types of data. So an OST opener may not be able to open all kinds of OST files. In this case, though, we only know of one specific use.

Outlook Exchange Offline Storage

The Microsoft Outlook email application uses files that contain the .ost file extension. The OST files store email messages that have been saved from an exchange server by the Microsoft Outlook application.

The OST files that Outlook uses are created when a user chooses the "Use Offline Folders" option in the Outlook application. When this option is selected, the application stores the folders on the local hard drive instead of on the actual mail server that the application would usually download the files from. These files are then saved with the .ost file suffix.

OST files are similar in nature to PST files, but OST files allow for larger file sizes.

We have not verified any programs yet that works with this specific format. If you know any, please use the 'Suggest a program' link below. Thanks!

OST file openers, viewers, etc.

These apps are known to open certain types of OST files. Remember, different programs may use OST files for different purposes, so you may need to try out a few of them to be able to open your specific file.

SysTools OST RecoverySysTools OST RecoveryUser submitted
On-Screen TakeoffOn-Screen TakeoffUser submitted
PSTViewer ProPSTViewer ProUser submitted
CoolUtils Outlook ViewerCoolUtils Outlook ViewerUser submitted
PST WalkerPST WalkerUser submitted
PSTViewer LitePSTViewer LiteUser submitted
SysTools OST Viewer version SysTools OST ViewerSysTools OST Viewer version SysTools OST ViewerUser submitted
We have not verified any programs that we know for certain can work with OST-files on Mac. If you know one, please use the Suggest link below and tell us about it!
We have not verified any online services that we know for certain can work with OST-files. If you know one, please use the Suggest link below and tell us about it!