What is OAB File Extension?


OAB stands for Offline Address Book which is a part of Microsoft Exchange Server accounts. The file extension is useful because it stores client's data like name, email address, and office address. As the name indicates, an OAB file can access even when it is not connected to the MS Exchange. OAB files backup is necessary. They are updated automatically in the server. MS Outlook in cached mode updates OAB once in a day.


They are Data File (Address Book).

Supportive Apps

MS Outlook and MS Exchange Server


It is the tech giant Microsoft created the file extension to store contact info.

MIME Types

It has one MIME type-



Location is primarily depended on the OS you are using.

In Windows 7/8/10-


In Windows XP and Server 2003-

drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook


The tech market offers to install OAB of version 2, 3 and 4.

The latest 4 version of OAB has-

  • Differential Patch file
  • Display template file & full detail file

How to open or view OAB File Extension

OAB files cannot be opened directly in the MS Outlook as an individual file. Users can take help of third applications to view OAB files.