What is OST File Extension?


OST stands for Offline Storage Table. It is well known for storing offline storage files in MS Outlook. The OST file extension gives users the flexibility to work even the server is down. The offline data can be updated to the Exchange Server as the connection of the network is established. OST files are photocopy or replica of Exchange Server Database. An OST file stores Emails, Contacts, Notes, Journals, and Tasks systematically.


OST files come under the category of Database Files.

Supporting Apps

It supports all the available versions of MS Outlook.


It is Microsoft takes care of the development and upgrading of the app.


Hexadecimal: 21 42 44 4e



The file extension saves automatically on different locations depending on the Outlook version you are using.

MS Outlook 2000 to 2003

C:\Documents and Settings\%username%\Local Settings\Application Data\Microsoft\Outlook\

MS Outlook 2007


MS Outlook 2013

C:\Users\%username%\Documents\Outlook Files

How to open or view OST File Extension

Users can manually open OST files by following a few simple tips.

Create a new OST file and use Outlook Data Files to access OST. The method will open a new copy of files showing emails in Outlook.

There are some free and paid viewers that can help you to view OST files.

Preferred conversion from OST