A Skype DAT file is a data file for the Skype program that holds "Chatsync" data; you can open it with the free Skype Chatsync Reader program. DAT files are used for analysis of computer forensics by law enforcement agencies to uncover and classify chat information. The Skype Chatsync Reader opens the DAT file in a readable format, and includes date and time stamps on chat conversations, as well as the contact IDs attached to each message.
Download and install Skype Chatsync Reader from itsecuritylab.eu.
Right-click on the DAT file to show the context menu.
Click the "Open With" option.
Select the "Skype Chatsync Reader" from the programs list. The DAT file opens in the Skype Chatsync Reader program.