Bl.ock is a simple viewer for sharing code examples hosted on GitHub Gist. For example, if your Gist URL is: https://gist.github.com/mbostock/1353700 Replace “gist.github.com” with “bl.ocks.org” in the URL to view it: https://bl.ocks.org/mbostock/1353700 It has configurations to determine how your block will be displayed. Bl.ock runs your visualization code (usually is d3) and displays it, unlike github that only displays the code.