Panel is an open-source Python library that lets you create custom interactive web apps and dashboards by connecting user-defined widgets to plots, images, tables, or text. Panel provides tools for easily composing widgets, plots, tables, and other viewable objects and controls into custom analysis tools, apps, and dashboards. Panel works with visualizations from Bokeh, Matplotlib, HoloViews, and many other Python plotting libraries, making them instantly viewable either individually or when combined with interactive widgets that control them. Panel works equally well in Jupyter Notebooks, for creating quick data-exploration tools, or as standalone deployed apps and dashboards, and allows you to easily switch between those contexts as needed.