You can pull just what you need from a large set of reusable UI widgets and controls, and from lower-level utilities for DOM manipulation, server communication, animation, data structures, unit testing, rich-text editing, and more. The Closure Library is server-agnostic, and is intended for use with the Closure Compiler. At Google, it's used in Web Search, Maps, YouTube, Google Plus, Gmail, Docs, Sites, Books, Blogger, Calendar, Picasa Web Albums, and more. Downloads. Accessibilité. The Programming Language Lua.