Identify, Fix and open files which Microsoft Windows can't open

Open OST file extension

File Type: (Text file)

Compatible with (WinXP, Vista and Win7)

Home Find file extension (eg.: .doc,.png)

File extension errors generally occur when the appropriate program is not installed in your system or your registry may be corrupt. You can either

Notes about the .OST file extension:

.OSTOST file is a Microsoft Outlook Offline Folder file; contains e-mail messages saved by outlook from an exchange server. OST file is almost same as (PST) Personal Folder File, it supports larger file sizes. To create OST file you need to select “USE OFFLINE FOLDERS” option in Outlook. File extension errors generally occur when the appropriate program is not installed in your system. Scan your system to identify and fix OST file extension errors.

Trouble opening OST files on Microsoft Windows?
Advanced File Optimizer
Need help opening a OST file? Advanced File Optimizer will do this for you. Opening a OST file only takes a few clicks and is very easy, even for novice users.
Compatible with Window XP, Vista, 7, 8, 8.1 and 10

Detailed information for file extension OST :

Primary association: Exchange

Company: Microsoft Corporation

Identifying characters Hex: 21 42 44 4E , ASCII: !BDN

Program ID: OSTFile , WEBFile

Reference: OST on Wikipedia , view more extensions

File type OST's association with other applications are:

  • On-Screen Takeoff (Project) by On Center Software, Inc.

    On-Screen Takeoff is software used in creating takeoffs from digital and paper plans.

  • Outlook (Offline Storage File) by Microsoft Corporation

    The .PST file 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. This includes attempting to access an .OST file. 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. The identifying characters used for this association are - Hex: 21 42 44 4E , ASCII: !BDNProgram ID: OSTFile , WEBFile Related links: MS Knowledge Base Article

  • Tivoli Storage Manager (File) by IBM

    The IBM Tivoli Storage Manager family of offerings is designed to provide centralized, automated data protection that can help reduce the risks associated with data loss.

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Comments on "How to open OST File"


I am very delighted to have this's really a fast, efficient and safe solution to rid your File extension errors forever!


Get rid of error problem easily... Thanks a ton!

Mark Thomas

I had bugged for couple of months with a Windows pop up on my system telling me it can't find this file...installed this amazing software and fix this problem. Now my system working perfectly again!

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