The way I understand it, .rdl is a server controlled report and .rdlc is a client-side controlled report. You have to deploy an .rdl file to a report server and access it using that server.With a .rdlc report, you can create the report and use a ReportViewer control to run the report in your application.You have to rename .rdlc to .rdl first.). RDL files are fully compatible with the ReportViewer control runtime. However, RDL files do not contain some information that the design-time of the ReportViewer control depends on for automatically generating data-binding code.