File Extension PST

.PST File

File extension: PST
File type: Personal Folder File


Notes about the PST file extension:



To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened" (Windows 7) or "How do you want to open this file?" (Windows 10) if you double-click the file. There click on "More apps" and choose a suitable software to view such files on your PC or from email attachments.

The PST file type is primarily associated with 'Outlook' by Microsoft Corporation. This file includes all E-mail folders, addresses or anything else that Outlook 97, 2K or XP collects. It has a 2GB file size limit. When approaching the 2GB limit, if Office SP-1 is not installed, Outlook becomes extremely unstable to the point of not being able to clicking on any message, folder, etc. without locking Outlook. To shrink the file, delete items from their folders and then clear the Deleted Items folder using Tools | Empty Deleted Items Folder. Outlook will compress the folder in the background while the computer is idle so you may not see a size decrease immediately.

Microsoft has a free add-in for backing up PST files. Microsoft also has a tool called Exchange 2000 Tool: PST2GB which will repair a PST file that is too large. USE CAUTION with this tool as it simply truncates the file to a size Outlook can handle and MAIL WILL BE LOST in the process.

You can make the PST file portable (maybe on a USB device) by doing the following. (1) Make certain Outlook is not using the PST file (usually directly after a restart with Outlook not loaded). (2) Copy the PST file to the USB device (or other location you want for the file) and rename the original so Outlook can't find it (be certain to change the extension from PST but save the file as a backup to the copy you made). (3) Start Outlook and when it complains it can't find the PST file and asks where it is point it to the new location for the file (USB device or whereever you wanted it). Outlook should then always look for the file in this location so you can move it from computer to computer this way.

Detailed information for file extension PST:


Primary association: Outlook
Company: Microsoft Corporation
Identifying characters Hex: 21 42 44 4E , ASCII: !BDN
Program ID: PSTFile , webfile , WEBFile
Related links: MS Knowledge Base Article, Outlook Recovery Toolbox, Outlook Express Repair, Outlook 2003 Add-in: Personal Folders Backup, Exchange 2000 Tool: PST2GB

Other applications associated with file type PST:

  • Yamaha (Pianist (Solo Piano) Style) by Yamaha Corporation of AmericaThis file type is used by the Tyros2 and other high-end Yamaha keyboards. This association is classified as Audio. The identifying characters used for this association are - Hex: 4D 54 68 64 , ASCII: MThd

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File Identifier - TrID
'Identifying characters' used on FILExt.com are
provided by Marco Pontello from his TrID database




To change file associations press Windows Key + X and then Apps and Features > Default apps > Choose default apps by file type. Invalid file associations could be the result of underlying issues within your Windows PC.

Technical data

To view technical data on file-extension PST click this link to expand/hide the additional area.

System Info for File Extension .PST

The following listing is compiled from the database produced by the 'Associate This!' program, selected data from the main FILExt database and information FILExt collected directly from user systems.

ProgramID: XnView.Image
EXEFile: %ProgramFiles%\XnView\xnview.exe %1

ProgramID: PokerStove.Document
EXEFile: %ProgramFiles%\POKERS~1\POKERS~1.EXE /dde


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