Learn Difference between PST and OST file in Outlook 2016

Shini Mohan | Published: August 4, 2016 | Exchange Server 2016, General Info | 3 Minutes Reading

Microsoft office is a popular productivity tool for Windows and Mac. It provides Word, PowerPoint, Excel, Outlook, and other productivity tools. Out of which, MS Outlook is one of the popular Mail Client, which manages various email accounts. It is the only platform, which allows business users to work in offline and online mode. It stores all its data in a propriety file known as PST file. However, when it is used in Offline mode it stores all its data in OST file format. Even though OST and PST files belong from the same parent application, they greatly vary from each other, both in their structure and working. In the following section, we will discuss the difference between PST and OST file; it will help to have more clear understanding about both.

Major Difference Between PST and OST File

OST File PST File
OST is Offline Storage Table. An offline table is created by MS Exchange to hold offline copies of email messages, calendar entries, contacts, task and so on. PST is Personal Storage Table. It is a file format that is used by Outlook to save all Outlook data that includes all email messages, tasks, contacts, etc.
It is the replica of Server folders and it is known as Slave replica of server. It is self-contained, standalone, structured binary file format that represents storage of message comprising arbitrary hierarchy of folder objects.
It can be accessed only through the MAPI profile, which originally created it. It is created with POP3 account, when it is connected with POP3 account.
OST file can be accessed when you are not connected with Exchange Server. You can easily edit, delete, or compose email message and when you will get online; it will synchronize automatically with Server. In Outlook, you can store PST file anywhere on system, which makes easy to keep backup of PST files or move it from one system to another.
OST file folder is useful in areas where internet connectivity is unreliable or limited. It is not suited for use in areas with limited or unreliable connections.
Its location in Windows 7/8/10 is:
Windows Vista: drive:\Documents and Settings\user\Local Setting\Application Data\Microsoft\Outlook
Its location in Windows 7/8/10 is:
Windows Vista: drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook

OST files provide the flexibility to work offline. It is mainly preferred by users for keeping their work in safe and secure form. If users are working offline then, they will never lose their work, no matter the Exchange server is connected or not. If Exchange database, is corrupted and reached in an unrecoverable state then, users can retrieve data from OST stored on the hard drive. Whereas PST files help, the end users in expanding the storage space s per requirement of data storage. User can also split the PST file by size, date, etc. that helps in management of Outlook and avoids corruption of PST file.


In the above discussion, major difference between PST and OST file in Outlook 2016 is discussed. It helps users to have the proper understanding between the features offered by the file format of Outlook, i.e. OST and PST. As you know that the emails and other data items is really very important for a user. Therefore it is necessary to know about the file systems of emails.

I hope that you would have understood about the the difference between PST and OST file now.