A web-accessible interface which allows code to be written in the web page and then run through an interpreter, with the subsequent output displayed; for NANOGrav, the Notebooks are set up for Python 3 and also Python 2, and have accessible to a variety of compiled code via Python bindings. This technology is sometimes referred to as “iPython Notebooks” but is now subsumed into the more general Jupyter project. Available at https://notebook.nanograv.org.