Learn What is PST File Format?

Outlook is the most significant email client application developed by Microsoft which is used .pst file extension to store email data. PST stands for Personal Storage Table it stores entire personal information. It is well-known as Outlook data file containing all components like emails, attachments, tasks, calendars, and much more to manage users personal data. There are some technical aspects of the PST file format as mentioned below:

A Brief Introduction of Outlook PST Format

Developer Microsoft
File Signature 21 42 44 4e
MIME Type Application/vnd.ms-outlook
Format Type Text & Binary
Supporting OS Microsoft Windows
File Category Email File
File Format .pst

Different Types of PST File

PST file is the most reliable format utilized by Microsoft Outlook to save all data in it. Outlook PST file extension can be broadly categorized into the following two file types:

1.ANSI: Such PST file types are generated in MS Outlook 2002 and its Previous versions also having 2GB file size limitation.

2.Unicode:Unicode type of PST is created in MS Outlook 2003 and Outlook 2003, 2007, 2010,2013, etc versions. The standard size of Outlook PST varies according to the edition of MS Outlook for example:

Outlook 2003 & 2007 has 20 GB file size limit and Outlook 2010 & 2013 has 50 GB size, which can increase or decrease to make changes to the registry.

Location of Outlook PST Data File

By default, the location of PST file varies based on Operating System that has covered below:

1. For Windows 8 users


2. For Windows 7 / Windows Vista users

drive:\Users\\Documents\Outlook Files

3. For Windows XP users

drive:\Users\\My Documents\Outlook Files

Users able to change the location of these data files as per their choice. Basically, time is required to modify the location of mailbox size.

Structure of PST File Format

The PST file encloses the binary data file and at the logical level, the MS-PST file contains the three different attributes:

1. NDB: The Node Database Layer (NDB) comprises the file allocation like info, header and the blocks that contain the message data. It can also use two B-trees such as N-Btree (Node Btree) and B-Btree (Block Btree) to locate the data.

2. LTP: This LTP layer keeps the Lists, Properties, and Tables inside the two-dimensional tables.

3. Messaging Layer: Messaging attribute has logic to combine two layers into folders such as message properties and attachments as well.


PST is the most significant data file of Outlook to manage all the personal information. For understanding the specification of .pst file extension, we have already presented the entire information to let the users more clear about what is PST file Format.