LocalDB is a lightweight version of the SQL Server Express Database Engine created specifically for developers. It starts on demand and runs in user mode, so there is no complex configuration. By default, LocalDB database creates “*.mdf” files in the C:/Users/ directory.
We support LocalDB directly in our products! You don't need separate drivers and can immediately connect to your database.
Developers for whom LocalDB is enough don't need to install and manage full instance of SQL Server Express. It offers T-SQL like standard SQL Server does and is a good embedded database. It doesn't create Windows services at all, LocalDB processes are started and stopped as needed.
SQL Express LocalDB can be considered as a next logical step from SQL Server Compact (SQLCE) when you need a truly powerful embedded database.