OST vs PST: Difference and Comparison

You’ll know about the PST and OST files if you are a Microsoft 365, MS Exchange Account, POP3 or IMAP account user.

PST and OST are the data storing files for such servers. You can easily convert an OST file to a PST one and vice versa according to the requirement.

Key Takeaways

  1. OST (Offline Storage Table) is an offline copy of data stored on a local computer, while PST (Personal Storage Table) is an Outlook data file.
  2. OST is used in a collaborative environment, while PST is used for personal email storage.
  3. OST files are synchronized with the server, while PST files are not and are more susceptible to data loss or corruption.


The difference between OST and PST is that OST files store data for offline utilization while the PST format saves data in the user’s local drive. An OST file is protected with a .ost extension, while a PST file is saved with a .pst extension.


OST files create the possibility for Outlook to work offline and automatically sync to Outlook when having access to an internet connection. It can also be used in an MS exchange server in an exchange environment.


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This enables the clients or users to compose, delete, read, and reply to emails offline.

Whereas PST mode cannot be used in an MS exchange server but is used on other servers. HTTP and IMAP use only PST folder files.

Your emails, journals, contacts, calendars, and other mailbox components saved locally are stored in the PST format.  

Comparison Table

Parameters of ComparisonOSTPST
Server compatibilityCompatible with all Exchange server versions.Compatible with other servers other than MS Exchange server.
PortabilityServer dependent and can’t be ported.It is portable and can be located anywhere on any local system.
Dependency factorIt can’t be transferred from the Exchange server individually.Possible to separately make a database Outlook file.
Sync possibilityData gets automatically synced when provided with a net connection.No auto-syncing can be done.
BenefitsThey are used when users want to work with domains where the net connection is low/poor.  Utilized when users want to have a backup of Outlook components.

What is OST?

OST is your offline file mode in MS outlook. Offline Storage Files draft the user’s mailbox data for offline mode on the local system. It does so by registering with Exchange Server taking Microsoft Outlook in use.

It is automatically made during the first use of Microsoft Outlook with server connectivity. Once the folder is composed, the data get arranged with the mail server for offline availability.

Clients can make mail and other data components in OST format even offline, but the data won’t be synchronized when offline.

Once your server is connected to an internet connection, the local copy and the server will be at the same pitch to sync information. 

The contents that the OST format can sync are:

  1. Headers: Descriptive identifiers that will give the sender name, message subject line, message receiving time and the message size.
  2. Full items:  Includes the header and message body with any attachments like pictures or objects. You can delete, add or change the things in the offline file.

You can also port items between folders, view your public offline folder’s content, and send messages in your offline Outbox.

Also, new messages are saved in the server inbox, and other users can delete, add or change contents in the folder.


What is PST?

In the computing language, PST or Personal Storage Table is an exclusive file format created by Microsoft to save copies of calendar events, messages and other components in their software program like Windows messaging and Microsoft Outlook.

The merit of PST is that they are easily portable and can be moved from one Outlook user to another. While owning the portability advantage, it also has a few security issues.

PST files are not designed to work as multi-gigabyte email archives. Due to this, subsequent data loss and corruption can be a recurring occurrence.

PST files also own emails that can’t be archived nicely. They are, thus, not always put into an appropriate retention classification system or deletion.

With that, PST files can be password protected, but a simple search on the net can discover many programs that could easily crack the passwords you’ve kept. This puts the client’s data at risk.

PST files are frequently used mail storing format, underlying all email solutions of Microsoft. In any Microsoft-based surrounding, getting how to manage and secure PST files is vital for blocking legal issues, attacks or data loss utilizing archived mail data.


Main Differences Between OST and PST

  1. OST is called Offline Storage Folder, while PST is called Personal or Online Storage Folder.
  2. OST files let the user read, reply, compose and view the emails even offline, whereas, in the PST file format, you can’t enjoy the advantage of such a feature.
  3. OST files support the Microsoft exchange server. As for the PST file format, you can use the exchange mode (though not recommended).
  4. OST files could be worked upon online and offline, while PST could be used for the files and data that are saved locally. 
  5. OST depends solely on the account configuration and can’t be opened individually. As for PST, there is no such feature found. 
Difference Between X and Y 2023 04 25T081654.516
  1. https://www.convertost.org/exchange-installation-and-recovery.pdf

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