Microsoft Outlook Personal Folders (Unicode)

Summary

Name

Microsoft Outlook Personal Folders (Unicode)

Version

2003-2007

Identifiers

• Library of Congress Format Description Identifier: fdd000378
• PUID: x-fmt/249

Description

The Personal Folders File or PST is an open proprietary data file format used to store local copies of messages, calendar events, and other items within Microsoft software including Microsoft Office Outlook. PST files are used to store archived items and to maintain offline availability of the items. PST is a stand-alone, self-contained, structured binary file format that does not require any external dependencies. Each PST file represents a message store that contains an arbitrary hierarchy of Folder objects, which contains Message objects, which can contain Attachment objects. Information about Folder objects, Message objects, and Attachment objects are stored in properties, which collectively contain all of the information about the particular item. PST_Unicode is the default format used by Office Outlook versions starting with Outlook 2003 and includes Outlook 2007, Outlook 2010 and Outlook 2013. It employs the Unicode character set. The file size constraints for PST_Unicode are significantly larger than the PST_ANSI overall size limit of 2 gigabytes (GB). PST_Unicode can support file sizes up to 20 GB in Outlook 2003 and Outlook 2007 and file sizes up to 50 GB for Outlook 2010 and Outlook 2013. According to Microsoft, these file size limits can be extended but would negatively impact performance.

Note

https://www.loc.gov/preservation/digital/formats/fdd/fdd000378.shtml; Format details: http://msdn.microsoft.com/en-us/library/ff385210%28v=office.12%29.aspx . Format specification from Microsoft that covers both PST_ANSI and PST_Unicode files.

File extensions

pst

Source

Digital Preservation Department / The National Archives

Internal signatures

Changelog

• Updated in V120

  Release date

  25 February 2025

  Microsoft Outlook Personal File (Unicode) 2003-2007: New description, library of congress fdd identifier and notes added. Submitted by Library of Congress.