I have always thought the different between RDL and RDLC is that RDL are used for SQL Server Reporting Services and RDLC are used in Visual Studio for client side reporting.The implemenation and editor are almost identical. RDL stands for Report Defintion Language and RDLC Report Definition Language Client-side. have always thought the different between RDL and RDLC is that RDL are used for SQL Server Reporting Services and RDLC are used in Visual Studio for client side reporting.