The .ACCDB file extensions are the database files of Microsoft Access 2007 and 2010. The database file with the file extension ".accdb" cannot be access with the versions of Microsoft Access prior to that of 2007. An ACCDB database file format is embedded with some new features such as multivalued fields, data macros, attachment embedding and many more. Microsoft Access is a database management system and is available as a part of Microsoft Office suite. Only Microsoft Access 2007 and 2010 versions support .ACCDB file format/extension.