OST vs PST: Know differences between OST and PST

Sristi Rana
Sristi Rana

Updated On - May 7, 2024

Summary: Sometimes, users get confused between an OST file and a PST file. OST file is an offline folder in Outlook, whereas a PST file is a personal storage table used to store data locally on a hard drive. In this article, you will get to know about the difference between an OST and a PST file. If you want to convert your OST file to a PST, then we recommend you use Recoveryfix for OST to PST Converter tool.

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Microsoft Outlook is one of the most used email applications these days. It is used to store emails, contacts, calendars and for task management. It’s like your personal assistant in this digital world which makes your work easy. It’s a handy application to stay organized and keep things on track.

Outlook uses two file formats, OST and PST, which store data locally and offline on your device’s hard disc. These files are specific to Microsoft Outlook and are very useful, as they store emails and other related data in them. They can help in retrieving the data when the file gets corrupted.

What is an OST file?

OST stands for Offline Storage Table. It is used by Outlook to store offline copies of your mailbox data, allowing you to access your emails and contacts. At the same time, the changes that you have made offline will synchronize automatically when your Exchange Server gets connected to the internet. It is a very useful feature; even without any internet connection you can work easily without facing any issue. When users use Outlook 365, Internet Message Access Protocol (IMAP) Outlook stores information in .ost format.

Advantages of OST file
  • You can easily access your OST file when you are offline.
  • There is no chance of data loss as data is stored offline on your system.
  • OST files are vulnerable and have less chance of getting corrupted.
Disadvantages of OST file
  • OST files are only supported in Microsoft Exchange Server.
  • OST files may become unavailable while having issues in syncing. In this scenario, you need to convert your OST file to PST file when OST file becomes inaccessible.
What is a PST file?

PST stands for Personal Storage Table. It is used to store contacts, emails, events, and calendars locally on your system’s hard disc. PST file is commonly used for archiving and backing up email data and to store a separate copy of mailbox data. When users use a Post Office Protocol (POP) account, Outlook creates a file in .pst format.

Advantages of PST file
  • Users can access multiple PST files at a time.
  • While exporting to an OST mailbox, Outlook provides password protection for more security.
  • It can be easily imported to any Outlook account.
Disadvantages of PST file
  • PST files can easily get corrupted or damaged.
  • You can access a PST file only when you are online.

OST and PST files are different from each other. The comparison between OST and PST files are listed below:

Parameters OST (Offline Storage Table) PST (Personal Storage Table)


OST files are used to access mailboxes even when you are not connected to the internet.

PST files are used for archiving, backup, and to keep a separate copy of your mailbox.


The changes that are made offline get automatically synced when you are connected to the internet.

They are independent of the server and don’t get synced automatically with it.

Size limit

OST files have a size limit determined by the exchange administrator. They can grow according to the size of your mailbox.

PST files have a default size limit of 2GB in Outlook’s 2002 and earlier versions, 20GB in 2003 and 2007 versions, and a maximum file size of 50GB in 2010 and later versions.


OST files are attached to a specific email account and can only be accessed by using that email account only.

PST files can be accessed easily with any Outlook profile.

Corruption problem

OST files can’t get corrupted or damaged easily.

PST files can get easily corrupted or damaged.

In-built tools for repairing

ScanOST.exe is used to fix errors and issues in files.

ScanPST.exe is used to fix errors and issues in files.

Import and export

OST files can’t be imported and exported easily as they can be accessed with specific email account only.

PST files can be exported and imported into any Outlook account.

Why to convert OST to PST file?

There can be some situations when there is a need to convert your OST file to PST file. Few of them are listed below:

  • Data recovery: When your exchange server becomes inaccessible, or your OST file becomes corrupted then converting them to a PST file is a better option
  • Offline access: PST files can easily be accessed offline. It allows you to manage your emails, contacts, and other data without internet connection.
  • Email migration: When you are switching between different email client applications, converting your OST file to PST file allows you seamless transfer of data.


In this article, we have discussed the basic difference between an OST and a PST file. Both file formats have their separate importance. Sometimes, we need to export OST files to a PST file due to various reasons. You can use Recoveryfix for OST to PST Converter tool to convert your OST files to a PST file. It’s a convenient and user-friendly tool; you can export your files without facing any data loss or corruption issues.

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