The primary modern tool for viewing and interacting with .nb and .cdf files. Free download (Desktop & iOS).
The legacy viewer (now mostly superseded by Player) for reading/printing older notebook versions. Historical utility. Jupyter, Mathematica, and the Future of the Research Paper mathematica notebook reader
Technical documentation on the reader technology details how it uses "sandboxing" to restrict potentially risky code when opening notebooks from untrusted sources. Core Tools for Reading Notebooks Accessibility Wolfram Player The primary modern tool for viewing and interacting with