Millions of Google users worldwide use JavaScript-intensive applications such as Gmail, Google Docs, and Google Maps. Like developers everywhere, Googlers want great web apps to be easier to create, so we've built many tools to help us develop these (and many other) apps. We're happy to announce the open sourcing of these tools, and proud to make them available to the web development community.

Closure Compiler
Closure Compiler is a JavaScript optimizer that compiles web apps down into compact, high-performance JavaScript code. The compiler removes dead code, then rewrites and minimizes what's left so that it will run fast on browsers' JavaScript engines. The compiler also checks syntax, variable references, and types, and warns about other common JavaScript pitfalls. These checks and optimizations help you write apps that are less buggy and easier to maintain. You can use the compiler with Closure Inspector, a Firebug extension that makes debugging the obfuscated code almost as easy as debugging the human-readable source.

Because JavaScript developers are a diverse bunch, we've set up a number of ways to run the Closure Compiler. We've open-sourced a command-line tool. We've created a web application that accepts your code for compilation through a text box or a RESTful API. We are also offering a Firefox extension that you can use with Page Speed to conveniently see the performance benefits for your web pages.

Closure Library
Closure Library is a broad, well-tested, modular, and cross-browser JavaScript library. Web developers can pull just what they need from a wide set of reusable UI widgets and controls, as well as lower-level utilities for the DOM, server communication, animation, data structures, unit testing, rich-text editing, and much, much more. (Seriously. Check the docs.)

JavaScript lacks a standard class library like the STL or JDK. At Google, Closure Library serves as our "standard JavaScript library" for creating large, complex web applications. It's purposely server-agnostic and intended for use with the Closure Compiler. You can make your project big and complex (with namespacing and type checking), yet small and fast over the wire (with compilation). The Closure Library provides clean utilities for common tasks so that you spend your time writing your app rather than writing utilities and browser abstractions.

Closure Templates
Closure Templates grew out of a desire for web templates that are precompiled to efficient JavaScript.  Closure Templates have a simple syntax that is natural for programmers.  Unlike traditional templating systems, you can think of Closure Templates as small components that you compose to form your user interface, instead of having to create one big template per page.

Closure Templates are implemented for both JavaScript and Java, so you can use the same templates both on the server and client side.


Closure Compiler, Closure Library, Closure Templates, and Closure Inspector all started as 20% projects and hundreds of Googlers have contributed thousands of patches. Today, each Closure Tool has grown to be a key part of the JavaScript infrastructure behind web apps at Google.  That's why we're particularly excited (and humbled) to open source them to encourage and support web development outside Google. We want to hear what you think, but more importantly, we want to see what you make. So have at it and have fun!