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A fast, reliable asset pipeline, supporting constant-time rebuilds and compact build definitions. Comparable to the Rails asset pipeline in scope, though it runs on Node and is backend-agnostic. For background and architecture, see the introductory blog post.

For the command line interface, see broccoli-cli.

This is 0.x beta software.

Windows support is still spotty. Our biggest pain point is unreliable file deletion (see rimraf#72).


npm install --save-dev broccoli
npm install --global broccoli-cli


A Brocfile.js file in the project root contains the build specification. It should export a tree.

A tree can be any string representing a directory path, like 'app' or 'src'. Or a tree can be an object conforming to the Plugin API Specification. A Brocfile.js will usually directly work with only directory paths, and then use the plugins in the Plugins section to generate transformed trees.

The following simple Brocfile.js would export the app/ subdirectory as a tree:

module.exports = 'app'

With that Brocfile, the build result would equal the contents of the app tree in your project folder. For example, say your project contains these files:

├─ main.js
└─ helper.js

Running broccoli build the-output (a command provided by broccoli-cli) would generate the following folder within your project folder:

├─ main.js
└─ helper.js

Using plugins in a Brocfile.js

The following Brocfile.js exports the app/ subdirectory as appkit/:

var Funnel = require('broccoli-funnel')

module.exports = new Funnel('app', {
  destDir: 'appkit'

That example uses the plugin broccoli-funnel. In order for the require call to work, you must first put the plugin in your devDependencies and install it, with

npm install --save-dev broccoli-funnel

With the above Brocfile.js and the file tree from the previous example, running broccoli build the-output would generate the following folder:

└─ appkit
   ├─ main.js
   └─ helper.js

A larger example

You can see a full-featured Brocfile.js in broccoli-sample-app.


You can find plugins under the broccoli-plugin keyword on npm.

Running Broccoli, Directly or Through Other Tools


Shared code for writing plugins.

Plugin API Specification

This section needs to be updated. For now, see docs/ and the broccoli-plugin README.

Broccoli defines a single plugin API: a tree. A tree object represents a tree (directory hierarchy) of files that will be regenerated on each build.

By convention, plugins will export a function that takes one or more input trees, and returns an output tree object. Usually your plugin will be implemented as a class representing a tree, but it is recommended to make the new operator optional (example).

A tree object must supply two methods that will be called by Broccoli:

The .read method must return a path or a promise for a path, containing the tree contents.

It receives a readTree function argument from Broccoli. If .read needs to read other trees, it must not call directly. Instead, it must call readTree(otherTree), which returns a promise for the path containing otherTree's contents. It must not call readTree again until the promise has resolved; that is, it cannot call readTree on multiple trees in parallel.

Broccoli will call the .read method repeatedly to rebuild the tree, but at most once per rebuild; that is, if a tree is used multiple times in a build definition, Broccoli will reuse the path returned instead of calling .read again.

The .read method is responsible for creating a new temporary directory to store the tree contents in. Subsequent invocations of .read should remove temporary directories created in previous invocations.


For every tree whose .read method was called one or more times, the .cleanup method will be called exactly once. No further .read calls will follow .cleanup. The .cleanup method should remove all temporary directories created by .read.



When it is known which file caused a given error, plugin authors can make errors easier to track down by setting the .file property on the generated error.

This .file property is used by both the console logging, and the server middleware to display more helpful error messages.

Descriptive Naming

As of 0.11 Broccoli prints a log of any trees that took a significant amount of the total build time to assist in finding which trees are consuming the largest build times.

To determine the name to be printed Broccoli will first look for a .description property on the plugin instance then fall back to using the plugin constructor's name.


  • Do not run broccoli serve on a production server. While this is theoretically safe, it exposes a needlessly large amount of attack surface just for serving static assets. Instead, use broccoli build to precompile your assets, and serve the static files from a web server of your choice.

Get Help

  • IRC: #broccolijs on Freenode. Ask your question and stick around for a few hours. Someone will see your message eventually.
  • Twitter: mention @jo_liss with your question
  • GitHub: Open an issue on a specific plugin repository, or on this repository for general questions.


Broccoli was originally written by Jo Liss and is licensed under the MIT license.

The Broccoli logo was created by Samantha Penner (Miric) and is licensed under CC0 1.0.


Browser compilation library – an asset pipeline for applications that run in the browser







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