Difference Between OST and PST File, OST vs PST

MS Outlook is a personal information manager application managed by Microsoft. It is a suite product of Microsoft Office that allows users to manage their emails,

calendars, tasks, contacts, notes, journals, and web browsing. Although, if you are an MS Outlook user, you are very familiar with OST and PST files (OST vs PST), which stand as Offline Storage Tables (OST) to save data for offline use and Personal Storage Table (PST) to store data on the client’s local disk.

Accounts such as Outlook 365 accounts, Exchange accounts, IMAP accounts, and Outlook.com accounts saved their data in Offline Outlook Data Files(.ost). On the other hand, accounts like POP accounts stored their data in Outlook Data Files(.pst). In this blog, we will discuss the primary difference between OST and PST files and which is better for users to save their data for further access. However, suppose you need to convert OST to PST files for migrating data from one place to another, or you want to move your essential data to a different system, then you can try a professional utility- Best OST to PST converter, which allows users to convert single and multiple OST files into PST format.

What is Offline Outlook Data File (.ost)?

OST stands for Offline Outlook Data Files, as it contains data in them and provides offline access to the users. It is used by IMAP accounts, Microsoft 365 accounts, Exchange accounts, and Outlook.com account users to store and synchronize copies of their mailbox information on your local computer.

OST file provides the facility to access all emails, calendar data, contacts, and tasks offline in the case when your connection to the mail server is interrupted or unestablished. Moreover, you can also read messages, compose an email, create appointments, and add contacts. While your connection gets established again, the changes you made will automatically get synchronized on your account mailbox. But what if you do not have Outlook or Exchange setup on your computer? In that case, you can use the OST file Viewer, enabling users to view corrupt, inaccessible, damaged, or healthy OST files without requiring any application.

What is Outlook Data File (.pst)?

An Outlook Data File (.pst files) stores information and other Outlook data items and backups them on your computer. A POP account is a type of account that one can create to add an account with different email services. It will download all your mailbox information from the mail server and save them directly to your computer or mobile device.

PST files offer features for backing up or exporting items from any email account. Some crucial data are email messages, calendars, contact, and task data. Note: There is no option to import the Offline Outlook Data File(.ost) file.

Due to these files being stored on your computer, it does not affect the mailbox size limit of your mail server. In addition, Outlook also provides an export/import feature with the help of which one can easily backup PST files on their local machine to free up storage space and import it when required. But sometimes, it is also possible that your Outlook is not working, or you won’t have Outlook installed to open the PST file. In that case, you can use the Free PST file viewer to read, open and view the PST file without MS Outlook.


The OST and PST are both Outlook Data formats to store the mailbox data items. An OST is an offline file created by Microsoft Outlook and Server to store data in offline copies, while PST is created by Outlook and allows users to transfer them from one system to another quickly. Users want to create it to store emails, contacts, calendar entries, and other mailbox items. Now, let’s learn the basic difference between OST and PST files (OST Vs PST).

Offline Outlook Data File (.ost) Outlook Data file(.pst)
OST file offers users an option to access and manage it without connecting with the Exchange Server in offline mode. However, the changes automatically synchronize with the Exchange Server mailboxes when the connection is established again. It keeps copies of mailbox items and updates them on the email server. PST file does not allow users to perform these processes; it is created when someone wants to take the backup of Outlook mailbox items.
Outlook 365 accounts, Exchange accounts, IMAP accounts, and Outlook.com accounts use OST files to store their information. Types of accounts, such as POP and IMAP, use PST files to store their information.
OST file created with encryption, i.e., MAPEntryID GUID key, and users need to first take permission with the linked MAPI profile for sharing it. Therefore, users won’t be able to access or import the OST file in other Outlook profiles. You can easily import or access PST files on other Outlook profiles.
Changes made in the OST file are automatically synchronized and appear on the server without downloading. In the case of a PST file, you need to download it for separating locally.
OST file is not corrupt or damaged easily, but due to malware or virus intrusion, system crash, synchronization errors, profile corruption, and other reasons, they may be inaccessible for users. A PST file can be easily damaged or corrupt for many reasons, like system crashes, large Outlook data files, etc.
You can repair the OST file with the ScanOST.exe tool; errors can also be fixed. You need to use the ScanPST.exe tool for PST files, which can also fix errors in PST files.
An OST file allows users to read, delete, compose, and edit email messages. The PST file does not allow you to edit the mailbox items in offline mode.

OST vs PST as both Outlook data file has their own benefits. PST file does not contain any option allowing users to access or make changes in offline mode. But on the same side, you will not migrate OST files into other accounts without the permission of the original MAPI profile. Thus, converting it into Outlook-compatible format, i.e., PST, has always been suggested to access and manage the OST mailbox items. Try the OST to PST tool to convert single or multiple OST files into PST file format.

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About Olaf Burch

Olaf works as a senior technology editor at Data Repair Tools. Fascinated by technology, he has more than 8 years of experience in the fields of data recovery, IoT, artificial intelligence and robotics. He enjoys the search and provision of DIY solutions to solve Windows technical problems. In spare time, he likes reading novels, and poetry. He also loves travel, rafting, trekking and so on.


  1. OST and PST both are the data files of Microsoft Outlook. There are many users of Outlook who really don’t know the difference and benefits etc., of these said files. The differences and features are described briefly and helpful to users who are not aware of these files and connections which works with which file.

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