Unicode vs. ANSI PST Files

DigiScope® can read data from, and write data to, ANSI and Unicode PST formats.


The Unicode PST format is the default for Microsoft Outlook 2003 and later.  Unicode PST files support multiple character sets, have no limitation in the number of items per folder, and have an increased file-size limitation of 20 GB, which is 10x the previous ANSI limit of 2GB.


In Outlook 2002 and earlier, the PST files are in the American National Standards Institute (ANSI) format and the overall size has a limit of 2 gigabytes (GB).  An ANSI PST that goes over 2 GB in size is vulnerable to corruption.

Many Outlook users want to know how to convert the ANSI PST (personal store) file they used with older versions of Outlook to the new Unicode format.  Unfortunately, you cannot directly convert a PST from Outlook97/2002's ANSI format to Unicode (or from Unicode to ANSI).  However, you can move, copy, or export the contents of an old ANSI message store to a new Unicode message store.