BNL files store netlist data, that is a list of all connections between various PCB elements. BNL is a filename extension associated with CAD software called MicroSim PCBoard developed by Cadence Design Systems.

The application is also known under the name OrCAD PCB Designer and is used for designing printed board circuits. BNL netlist files support PCB design by providing specifications and allow for better testing of various board components and their placement.