Background explorer simplifies or automates many of the tedious and error-prone tasks involved in creating a detailed radioactivity budget for a low background detector system. The tool also provides a rich web interface allowing even non-technical users to easily modify the model assumptions and drill-down into the model and result details. Backend: https://github.com/bloer/bgmodelbuilder Web application: https://github.com/bloer/bgexplorer Demo/user template: https://github.com/bloer/bgexplorer-demo