Thursday, March 17, 2011


Shrink And Compact Outlook PST File

This article describes how to compact the personal folders (.pst) files in Microsoft Outlook, to eliminate deleted item space and recover room on your hard disk.

To conserve space on your hard disk, you can delete unwanted items from the various .pst folders, and then compact the files to make them smaller.

When you delete the unwanted items from each folder, it only moves them to the Deleted Items folder, which is in the same file. You must delete the items from the Deleted Items folder to permanently delete them so that Outlook can compact the file.

The compacting process does not remove all the free space from the file. It leaves either 16 kilobytes (KB) or 4 percent of the file size (before compacting), whichever is greater.

To be compacted, a file must meet the following requirements:

  • The file must be 16 KB or larger.
  • The file must have at least 16 KB of space freed since the last time it was compacted.

You can start Outlook file compaction manually, or run it automatically in the background.

Automatic Background Compaction

Personal folders (.pst) files that are not on your computer may require manual compaction because of interactions between the computer where the .pst files are stored and your computer.

Automatic compaction takes place as an idle task in the background. The following conditions must be true for this background task to take place:

  • Outlook must be running.
  • The computer must not be engaged in other CPU-intensive tasks such as copying or downloading files.
How to Manually Start PST Compaction
  • On the File menu, click Data File Management.
  • Click the personal folders (.pst) files that you want to compact, and then click Settings.

For Windows Vista, the default path of .pst files is drive:\Users\user\AppData\Local\Microsoft\Outlook. For Microsoft Windows XP or Microsoft Windows Server 2003, the default path of .pst files is drive:\Documents and Settings\user\Local Settings\Application Data\Microsoft\Outlook.

  • Click Compact Now, click OK, and then click Close.


About bench3 -

Haja Peer Mohamed H, Software Engineer by profession, Author, Founder and CEO of "bench3" you can connect with me on Twitter , Facebook and also onGoogle+

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Write comments
Marshal Hubs
April 29, 2013 at 9:55 AM delete


If your Outlook PST file size becomes large then it may be possible you will lost your emails due to file corruption. Because Large size is one of the common issue of PST file corruption. So you have option to compact the PST file using above tips. If the problem still exist then you can compact your pst file using Stellar Phoenix Compact PST Software. It will compress your PST file without deleted your original data.