Your website should use far-future expires headers on static assets, to make the best use of client-side caching. But when a file is cached, updates won't get picked up. Cache busting is the practice of making the filename of a cached asset unique to its content, so it can be cached without having to worry about future changes. This gem adds a filter and some helper methods to Nanoc, the static site generator, to simplify the process of making asset filenames unique. It helps you output fingerprinted filenames, and refer to them from your source files. It works on images, javascripts and stylesheets. It is extracted from the nanoc-template project at http://github.com/avdgaag/nanoc-template.