OST File Type

- The quick facts

What are OST files and how to open them

Are you having problems opening an OST file or just wondering what they contain? We explain what these files are used for and show you software that we know can open or otherwise handle your files.

What is an OST file?

An .OST file is an Outlook Exchange Offline Storage file.

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 to PST files, but OST files allow for larger file sizes.

How to open OST files

We have identified 5 OST openers that are compatible with this specific type of OST file.

Programs that open Outlook Exchange Offline Storage files

Last updated: March 12, 2022

Various apps that use files with this extension

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.

On-Screen TakeoffOn-Screen TakeoffUser submitted
CoolUtils Outlook ViewerCoolUtils Outlook ViewerUser submitted
PSTViewer LitePSTViewer LiteUser submitted

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about OST file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.