PST vs OST: A Detailed Comparison

Personal Storage Table (PST) and Offline Storage Table (OST) are two file formats used by Microsoft Outlook for storing user data. Both have unique characteristics and serve different purposes in email management and data storage.

What is PST?

PST, or Personal Storage Table, is a file format used by Microsoft Outlook to store copies of messages, calendar events, and other items. PST files are most commonly used for storing archived items and are a popular choice for data backup and transfer.

Characteristics of PST Files:

What is OST?

OST, or Offline Storage Table, is a file format used by Microsoft Exchange Server, as well as the Outlook and Office 365 suite. OST files are an offline cache of what is stored on the mail server, allowing access to mail data even when not connected to the internet.

Characteristics of OST Files:

Comparison of PST and OST

Feature PST OST
Portability High (easily transferred) Low (tied to specific account)
Usage Scenario Backup, Archive Offline Access, Synchronization
Internet Requirement Not required Required for synchronization
Server Dependency No Yes
Size Limit Up to 50GB Unlimited, but performance varies


Choosing between PST and OST depends on the user's specific needs. If the goal is to create backups or transfer data between different systems, PST is the better choice. For users who need to access their mailbox offline and synchronize with a mail server, OST is more suitable.