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PST File Format

PST File — Complete Guide

A comprehensive guide to understanding PST files, their structure, how to open them, view their contents, import data into Outlook, and the best free tools available.

PST File Format Microsoft Outlook Email Archive Personal Storage .pst extension Windows
.PST

PST File Format

  • Extension.pst
  • DeveloperMicrosoft
  • CategoryEmail Archive
  • ANSI limit2 GB
  • Unicode limit50 GB
  • PlatformWindows
  • First released1997
1

What is a PST File?

PST stands for Personal Storage Table. It is an proprietary file format built by Microsoft Outlook to store copies of emails, contacts, calendars entries, and other mailbox data locally on a computer. It serves as a personal mailbox archive, allowing users to organize, backup, and manage their email data independently from the mail server. PST files employ a hierarchical structure to organize mailbox data, facilitating efficient storage and retrieval of individual items and folders.

📌
Full Form: PST = Personal Storage Table The PST format is also called "Personal Folders File" or "Outlook Data File." On disk it always ends with the .pst extension.

PST File — Version History

ANSI Format Outlook 97-2002

ANSI stands for American National Standards Institute. In Outlook 97, 98, 2000, and 2002, the PST files are in the ANSI format. The overall capacity or limit of the file is of 2GB. An ANSI PST that goes over 2 GB in size is vulnerable in corruption. ANSI PST files also have limited support for non-English characters.

Unicode Format Outlook 2003+

It is an advance format of PST. This is the default file format for Microsoft Outlook 2003 and all the above versions. Unicode PST files support multiple character sets and have no limitation in the number of items per folder. It has storage capacity of 20 GB in MS Outlook 2003 & 2007 and 50 GB in MS Outlook 2010, 2013 & 2016.

Modern PST 2010 - Present

Modern Outlook versions, including Outlook 2010, 2013, 2016, 2019, 2021, and Microsoft 365, continue to use the Unicode PST format in Outlook 2003 but with several enhancements. In these versions, the default PST file size limit was increased to 50 GB.

⚠️
ANSI vs Unicode PST Compatibility Newer Outlook versions can read ANSI PST files but won't allow creating new ones. To avoid corruption risks with old files, convert ANSI PST to Unicode using Outlook's built-in upgrade tool.
2

PST File Structure & Technical Specs

A PST file is a structured database file used by Microsoft Outlook to store mailbox data such as emails, contacts, calendars, notes, tasks, and attachments. A PST file is organized using a layered architecture that enables efficient data storage and retrieval. Its structure is logically arranged in three layers: the NDB (Node Database) layer, the LTP (Lists, Tables, and Properties) layer, and the Messaging layer.

NDB Layer: The NDB layer consists of a database of nodes, which represents the lower-level storage facilities of the PST file format. It consists of the header, file allocation information, blocks, nodes, and two BTrees.

LTP Layer: The LTP layer implements higher-level concepts on top of the NDB construct. The core elements of the LTP Layer are the Property Context (PC) and Table Context (TC).

Messaging Layer: The Messaging layer consists of the higher-level rules and business logic. It defines the rules and requirements that need to be followed when modifying the contents of a PST file.

Where is the PST File Stored?

The storage location of a PST file depends on the Outlook version, account type, and settings. Typical default paths are:

Default Locations 
Outlook 2007 and previous on Windows XP
C:\Documents and Settings\%username%\Local Settings\Application Data\Microsoft\Outlook\

Outlook 2007 and previous on Windows Vista, Windows 7, Windows 8 or Windows 10
  C:\users\%username%AppData\Local\Microsoft\Outlook\

Outlook 2010 on Windows XP
C:\Documents and Settings\%username%\My Documents\Outlook Files

Outlook 2010, Outlook 2013, Outlook 2016, Outlook 2019, and Microsoft 365 on Windows Vista, Windows 7, Windows 8, or Windows 10
C:\users\%username%\Documents\Outlook Files

The easiest way to find PST files is directly in Outlook:
1. File → Account Settings → Account Settings 
2. Select the Data Files tab
3. Click Open File Location
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Quick Tip: Find your PST file In Windows Explorer, search for *.pst in your user profile folder. Or open Outlook → File → Account Settings → Data Files tab — it shows the exact path of every PST file currently attached to your profile.
3

How to Open a PST File

There are three main ways to open a PST file, depending on whether you have Outlook installed or not.

1

Open MS Outlook on your system.

2

Go to File tab and click on Open & Export.

3

Choose Open Outlook Data File option.

4

Now, a file browser dialog will open.

5

Click on Browse and select PST file that you want to open and click OK.

The PST file will appear in the left sidebar folder pane of Outlook. Click on this file to access its data.

If you have not installed MS Outlook, then you can use a free PST Viewer tool to open and read PST file contents. There are lot of free PST Viewer tools like Yota Free PST Viewer available in the market to access PST file data.

1

Download and install the Yota PST Viewer Tool on your system.

2

Run the tool and click Open > Email Data Files > PST Files > Choose Folders.

3

Browse and Add the files from your system into the software panel.

4

Click on the file and view the email and its data in different preview modes.

4

What's Inside a PST File?

A PST files stores a complete copy of Outlook mailbox data in a single file.

Emails

PST files store email messages such as inbox emails, sent items, drafts, archived messages, and deleted emails. Each message retains its content, sender and receiver info, subject lines, and other email properties.

Attachments

File attached to emails, such as documents, images, video, audio, and PDFs are stored along with their respective messages inside the PST file.

Contacts

Contact information, including names, email addresses, phone numbers, and company details stored inside a PST file.

Calendar

Appointments, meetings, events, reminders, recurring schedules, and calendar entries are stored in PST files,

Notes

Outlook Notes created for reminders or personal reference can also be included in the PST file.

Tasks

To-do lists, assigned tasks, follow-up items, deadlines, and task-related details are stored within PST files.

Journal

Outlook Journal entries, which can track activities such as calls, emails, documents, and other interactions, may also be stored in a PST file.

Folder Structure

A PST file keeps the original mailbox folder hierarchy intact, including custom folders and subfolders.

How to View Specific Data Types

Data Type In Outlook In Free Viewer Export Format
Emails Folder pane → Inbox/Sent Left tree → expand folders EML, MSG, PDF, HTML
Attachments Open email → click attachment Preview pane → attachment tab Original file format
Calendar Events Calendar folder → click event Calendar folder in tree ICS, CSV
Contacts Contacts folder Contacts folder in tree VCF, CSV
Tasks Tasks folder Tasks folder in tree CSV, ICS
Notes Notes folder Notes folder in tree TXT, HTML
5

How to Import PST Emails into Outlook

You can easily import PST file into Outlook via the Import/export feature. Follow the below given steps:

⚠️
Opening vs Importing — What's the Difference? Opening a PST attaches it as a separate folder set in Outlook (non-destructive, read-only-ish). Importing copies the PST content into your primary mailbox — it merges everything. Use import only when you want data merged permanently.
1

Open Outlook and go to File tab.

2

Click on Open & Export and choose Import/Export option.

3

Select Import from another program or file and click Next.

4

Choose Outlook Data File (.pst) and press Next.

5

Browse and select .pst file from your system.

6

Choose the folders & subfolders to import and click Finish.

The Outlook will start importing PST data. If your PST file is large then it takes time to complete the process.

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Importing a Password-Protected PST If your PST file is password-protected, Outlook will prompt you to enter the password during the import. In case, you have forgotten the password, you can use PST Password Remover Tool that will help you to clear the password to complete the importing process.

Import PST to Gmail / Office 365

If you need to transfer your PST file to a cloud-based email service then configure your email service with Outlook and then import PST data into the configured account. On the other hand, you can use a migration tool to move PST emails to cloud service directly without any configuration.

6

Free Tools for PST Files

Whether you want to open, convert, repair, split, or remove password from a PST file, there are dedicated tools available for each purpose. Below are some widely used free options to help manage PST files efficiently:

Advik PST Converter

Free Trial

A Trustworthy tool to convert PST files into 30+ file formats. Easily handle large Outlook PST files and convert them without losing any information.

  • Dual mode to add single or multiple PST fules for conversion.
  • Convert PST file into multiple formats like MBOX, EML, MSG.
  • Import PST file to any cloud based platforms such as Gmail, Office 365.
  • Recovery Mode option for converting corrupted or damaged PST files.
  • Outlook installation is not required to convert PST file data.
Learn More

ScanPST (Inbox Repair Tool)

100% Free (Built-in)

Microsoft provides a free built-in tool i.e. SCANPST.exe also known as Inox Repair Tool to scan and repair PST file corruption issues.

  • Built-in free utility from Microsoft.
  • Repair minior PST file corruption issues.
  • Scan and fixes Outlook data file errors.
  • Creates a backup before repair.
  • Recover inaccessible emails and folders.
How to Use ScanPST

Yota PST Viewer

100% Free

A simple and effective tool to view, open, and read all the data of Outlook PST files including emails, contacts, attachments, etc. without installing Outlook application.

  • View PST data without any modification or alteration
  • Open corrupted or damaged PST file and extract data from it.
  • Different preview modes to access data from PST files.
  • Supports both ANSI and Unicode PST files.
  • No Outlook installation is required to read PST data.
Learn More

PST Password Remover

Free Trial

Remove the lost or forgotten password from PST files. The tool allows you to select single or multiple Outlook PST files for password removal.

  • Remove passwords from protected PST files.
  • Compatible with both ANSI and Unicode PST files.
  • Does not require the support of Outlook application.
  • Supports PSTs encrypted with special and non-English characters.
  • Recover long and complex passwords without altering PST data.
Learn More

PST Splitter

Free Trial

Divide large-sized PST files into smaller parts based on date, size, and folder.

  • Split the oversized PST file into multiple small files.
  • No file size limitations to divide large PST files.
  • Supports batch PST file splitting in a single process.
  • Supports batch PST file splitting in a single process.
  • Able to break down corrupted or inaccessible PST file.
Learn More

PST Merge Tool

Free Trial

Merge PST files into one unified file while keeping all email, contacts, and attachments intact.

  • Combine multiple PST files into one without data loss.
  • Remove duplicate items during the merging process.
  • Maintain all email attributes and folder structure.
  • Merge PST files without the need of MS Outlook.
  • Supports PST files of all Outlook versions.
Learn More
7

Common PST Problems & Fixes

PST File Corruption

Common

Abrupt system shutdown or crash, improper Outlook termination, faulty hardware/software issues, and virus or malware attacks may be the cause of PST file corruption.

Fix: Use Inbox Repair Tool
1. Navigate to ScanPST.exe Location.
2. Double-click on SCANPST.EXE to start the program.
3. Click on Browse to choose the damaged PST file.
4. Click on Start button to begin the scanning process.
5. If it finds errors then click on the Repair button.

Once the repairing is complete a popup will appear, click OK.

For severely corrupt files that ScanPST can't fix, use a professional PST Repair tool which can recover data even from heavily damaged files.

PST File Reached Size Limit

Frequent

When PST files get oversized like more than 20 or 50 GB, then there is a risk of PST file corruption.

Fix: Compact the PST File

  • Open Outlook on your system.
  • Navigate to File > Info > Account Settings > Account Settings.
  • Select the Data Files tab and choose the PST file and then click Settings.
  • Go to Advanced tab and click Outlook Data File Setting.
  • Click Compact Now.
  • The process take time depending upon the size of file

Password Protected PST Access Issues

Occasional

If you receive a password-protected PST file from another user or may have forgotten the password set by several years ago then it may be difficult to access its data.

Fix: Remove Password from PST File

  • Open Outlook on your system.
  • Click File > Account Settings > Account Settings.
  • Select the Data Files tab and choose the PST file and then click Settings.
  • Click on Change Password.
  • Type your old password, new password, and verify password and then proceed to OK.

If you have forgotten the password then Advik PST Password Remover Tool will help you to solve this issue.

8

Frequently Asked Questions

Yes, using PST Viewer Tool, you can open PST file without Outlook installation.

Yes, you can use automated PST Password Remover Tool to safely remove the password without requiring the original password.

No, the tool allows users to recover, reset, or remove password without making any changes or compromising the data.

There are several ways to reduce the size of a PST file like Use Outlook's Cleanup Tools, Compact Now PST, Delete large emails or attachments, use a PST Splitter Tool.

The maximum size of a PST file depends on the format. ANSI PST file size limit has 2 GB and the Unicode PST file size limit 50 GB.

C:\Users\username\AppData\Local\Microosft\Outlook. To quickly find your PST file location, open Outlook, go to File > Account Settings > Data Files and click Open File Location.