Sprockets is a Rack-based asset packaging library that serves as the core of the Rails asset pipeline. It compiles, concatenates, minifies, fingerprints, and serves JavaScript, CSS, images, fonts, and other static web assets. The architecture is modular: an `Environment` object manages load paths, processors, transformers, compressors, and exporters; a `Manifest` compiles assets to disk with digest filenames; and a `Server` provides a Rack endpoint for development. Assets flow through a pipeline of preprocessors (e.g., ERB, CoffeeScript, Babel), transformers (MIME type conversions), postprocessors, bundle processors (concatenation), and optionally compressors and exporters (gzip, file write). The library supports source maps, caching with dependency tracking, and extensible registration of custom processors, transformers, and compressors. It is a mature, well-architected library with clean abstractions and high reusability, though it carries some legacy components (e.g., YUI compressor, Sass importer) and optional external gem dependencies.