>> OST file

OST file format description

Many people share .ost files without attaching instructions on how to use it. Yet it isn’t evident for everyone which program a .ost file can be edited, converted or printed with. On this page, we try to provide assistance for handling .ost files.

1 filename extension(s) found in our database.

.ost - Microsoft Outlook Offline Folder File

The OST data files are related to Microsoft Outlook. OST file is a Microsoft Outlook Offline Folder File.

Microsoft Outlook
Data files
- / -
Microsoft Outlook Offline Folder File related extensions:
Microsoft Office IME Search Provider Definition
Microsoft Graph 5 Data
Microsoft Access JET Database
Office Open XML File
Lacerte Tax Data
Microsoft Office Language Specific Resources

Naturally, other applications may also use the .ost file extension. Even harmful programs can create .ost files. Be especially cautious with .ost files coming from an unknown source!

Can't open a .ost file?

When you double-click a file to open it, Windows examines the filename extension. If Windows recognizes the filename extension, it opens the file in the program that is associated with that filename extension. When Windows does not recognize a filename extension, you receive the following message:

Windows can't open this file:


To open this file, Windows needs to know what program you want to use to open it. Windows can go online to look it up automatically, or you can manually select one from a list of programs that are installed on your computer.

To avoid this error, you need to set the file association correctly.

The .ost file extension is often given incorrectly!

According to the searches on our site, these misspellings were the most common in the past year:

os, kst, owt, ot, osh, lst, st, ist, pst, oxt, ots, osr, osg, oct, sot

Is it possible that the filename extension is misspelled?

Similar file extensions in our database:

TheWord Old Testament Text Module
ObjectScript Source Code
GCC Assembler Listing File
E-Sword v8 Verse List
Olivetti Olitext Plus Script
OneWorldTree Data

Operating systems currently supports the following operating systems:

Windows XP/Vista, Windows 7/8, Windows 10, CentOS, Debian GNU/Linux, Ubuntu Linux, FreeBSD, Mac OS X, iOS, Android

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If you have useful information about the .ost file format, then write to us!

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