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Updated: April 07, 2025

.PST File Extension

There is only one filetype that uses .PST file extension and it is Outlook Data File.

Outlook Data File

File category: Data Files
Developer: Microsoft
Open with: Microsoft Outlook (+2 more)
Platforms: Windows, macOS, iOS, Android

A PST (Personal Storage Table) file is a data storage format used primarily by Microsoft Outlook and Microsoft Exchange. These files store personal information including emails, calendar items, contacts, tasks, notes, and other Outlook data in a single, portable file.

Microsoft introduced the PST format in the early 1990s with early versions of Microsoft Exchange and Outlook. The format has evolved over time, with significant updates to accommodate larger file sizes and improved data organization.

How PST Files Are Used

PST files serve several important purposes:

  • Data Storage: They provide a way to store emails and other Outlook items locally on your computer
  • Archiving: Users often create PST files to archive older emails and reduce the size of their main mailbox
  • Backup: PST files allow users to back up important email data
  • Migration: They can be used to transfer email data when moving to a new computer or email system

Size Limitations and Performance

PST files have size limitations:

  • Older formats (ANSI) have a 2GB size limit
  • Newer formats (Unicode) have a theoretical limit of 50GB, though Microsoft recommends keeping files under 20GB

As PST files approach their size limits, Outlook performance can degrade significantly, causing delays and slower operation.

How to Open .PST as Outlook Data File

PST files can be opened with:

  • Microsoft Outlook: The primary application for working with PST files
  • Microsoft Exchange Server: For server-side management
  • Third-party viewers: Applications like PSTViewer Pro allow viewing PST content without Outlook

The format is supported on Windows and macOS systems but is not compatible with mobile platforms.

How to Convert an PST File

PST files can be converted to several other formats:

  1. Convert to Office 365/Exchange Online: Using Microsoft's migration tools
  2. Convert to MBOX: For use with other email clients like Thunderbird
  3. Convert to MSG or EML: For individual email messages
  4. Export to CSV: For contact information

Conversion tools include:

  • Microsoft PST Import Tool
  • Stellar Converter for PST
  • Various third-party email migration utilities

PST files work primarily with Microsoft products and have limited compatibility with non-Microsoft email clients without conversion. While the basic format is cross-platform compatible, the tools to work with PST files are primarily Windows-based, with some macOS support.

Applications That Open PST Files

Windows Apps for PST Files:

macOS Apps for PST Files:

iOS Apps for PST Files:

Android Apps for PST Files:

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