PST File Extension

Outline: What is PST file extension?

PST stands for Personal Storage Table. Outlook File(PST) is a facility provided by Microsoft Co. for file storage in order to keep entire Outlook data. Outlook data comprises Emails, Attachments, Notes, Contacts, Calendars items, Task, etc. Binary data file algorithm is used for constructing PST File and it is divided into three different layers: Messaging Layer, NDB (Node Database) and LTP. If we are using Microsoft Outlook, then our emails, attachments, calendar, tasks, and other items associated with our account are saved on a mail server, on our computer, or both. Outlook item which is saved on our computer, is kept in an Outlook Data File (.pst and .ost).

Application Category

This format of data storage comes under Database File Category.

Applications Supported

MS Outlook

Brief Introduction of Proprietor

Microsoft is the creator of Outlook and all the file formats associated with it. Since 1997, the year when the term Outlook was coined in the Tech World, Microsoft has updated Outlook many number of times. With the introduction of every new version, Microsoft increased functionality of Outlook.

Internal Structure of PST File

PST file's MIME Type


File Signature

hexadecimal: 21 42 44 4e

Different Types of PST Files in Outlook

ANSI(97-2002 Personal Folder File)

Default file format for older versions of Outlook (97–2002) is capable of holding only up to 2GB of data. It does not support multiple languages and structure is a 32–bit unsigned value.
However, Outlook still provides an option to create ANSI PST file even in its latest versions of Outlook while creating an Outlook file.


It is a multi-lingual data file format. It can handle data up to 50GB (massive amount of storage capacity) and it is 64-bit unsigned long. There is a limitation of UNICODE(2003-2016), that it can not run in older version of Outlook.

Location of PST Extension File

In Microsoft Outlook 2016

Outlook 2016: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\

In Microsoft Outlook 2013

Outlook 2013: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\

In Microsoft Outlook 2010

Outlook 2010: HKEY_CURRENT_USER\Software\Microsoft\Office\14.0\Outlook\

In Microsoft Outlook 2007

Outlook 2007: HKEY_CURRENT_USER\Software\Microsoft\Office\12.0\Outlook\

In Microsoft Outlook 2003

Outlook 2003: HKEY_CURRENT_USER\Software\Microsoft\Office\11.0\Outlook\

Note:- There is a universal method. We can find out the location of PST extension file using "Account Setting" option in MS Outlook's Settings.