16.2.8 • Public • Published


require('modules') in the browser

Use a node-style require() to organize your browser code and load modules installed by npm.

browserify will recursively analyze all the require() calls in your app in order to build a bundle you can serve up to the browser in a single <script> tag.

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getting started

If you're new to browserify, check out the browserify handbook and the resources on browserify.org.


Whip up a file, main.js with some require()s in it. You can use relative paths like './foo.js' and '../lib/bar.js' or module paths like 'gamma' that will search node_modules/ using node's module lookup algorithm.

var foo = require('./foo.js');
var bar = require('../lib/bar.js');
var gamma = require('gamma');

var elem = document.getElementById('result');
var x = foo(100) + bar('baz');
elem.textContent = gamma(x);

Export functionality by assigning onto module.exports or exports:

module.exports = function (n) { return n * 111 }

Now just use the browserify command to build a bundle starting at main.js:

$ browserify main.js > bundle.js

All of the modules that main.js needs are included in the bundle.js from a recursive walk of the require() graph using required.

To use this bundle, just toss a <script src="bundle.js"></script> into your html!


With npm do:

npm install -g browserify


Usage: browserify [entry files] {OPTIONS}

Standard Options:

    --outfile, -o  Write the browserify bundle to this file.
                   If unspecified, browserify prints to stdout.

    --require, -r  A module name or file to bundle.require()
                   Optionally use a colon separator to set the target.

      --entry, -e  An entry point of your app

     --ignore, -i  Replace a file with an empty stub. Files can be globs.

    --exclude, -u  Omit a file from the output bundle. Files can be globs.

   --external, -x  Reference a file from another bundle. Files can be globs.

  --transform, -t  Use a transform module on top-level files.

    --command, -c  Use a transform command on top-level files.

  --standalone -s  Generate a UMD bundle for the supplied export name.
                   This bundle works with other module systems and sets the name
                   given as a window global if no module system is found.

       --debug -d  Enable source maps that allow you to debug your files

       --help, -h  Show this message

For advanced options, type `browserify --help advanced`.

Specify a parameter.
Advanced Options:

  --insert-globals, --ig, --fast    [default: false]

    Skip detection and always insert definitions for process, global,
    __filename, and __dirname.

    benefit: faster builds
    cost: extra bytes

  --insert-global-vars, --igv

    Comma-separated list of global variables to detect and define.
    Default: __filename,__dirname,process,Buffer,global

  --detect-globals, --dg            [default: true]

    Detect the presence of process, global, __filename, and __dirname and define
    these values when present.

    benefit: npm modules more likely to work
    cost: slower builds

  --ignore-missing, --im            [default: false]

    Ignore `require()` statements that don't resolve to anything.


    Don't parse FILE at all. This will make bundling much, much faster for giant
    libs like jquery or threejs.


    Turn off builtins. This is handy when you want to run a bundle in node which
    provides the core builtins.


    Turn off setting a commondir. This is useful if you want to preserve the
    original paths that a bundle was generated with.


    Turn off bundling of all external modules. This is useful if you only want
    to bundle your local files.


    Alias for both --no-builtins, --no-commondir, and sets --insert-global-vars
    to just "__filename,__dirname". This is handy if you want to run bundles in

  --no-browser-field, --no-bf

    Turn off package.json browser field resolution. This is also handy if you
    need to run a bundle in node.


    Instead of the default package.json#browserify#transform field to list
    all transforms to apply when running browserify, a custom field, like, e.g.
    package.json#browserify#production or package.json#browserify#staging
    can be used, by for example running:
    * `browserify index.js --transform-key=production > bundle.js`
    * `browserify index.js --transform-key=staging > bundle.js`


    Alias for --bare and --no-browser-field.


    Turn off converting module ids into numerical indexes. This is useful for
    preserving the original paths that a bundle was generated with.


    Instead of standard bundle output, print the dependency array generated by


    Turn off deduping.


    Print each file in the dependency graph. Useful for makefiles.


    Consider files with specified EXTENSION as modules, this option can used
    multiple times.

  --global-transform=MODULE, -g MODULE

    Use a transform module on all files after any ordinary transforms have run.

  --ignore-transform=MODULE, -it MODULE

    Do not run certain transformations, even if specified elsewhere.

  --plugin=MODULE, -p MODULE

    Register MODULE as a plugin.

Passing arguments to transforms and plugins:

  For -t, -g, and -p, you may use subarg syntax to pass options to the
  transforms or plugin function as the second parameter. For example:

    -t [ foo -x 3 --beep ]

  will call the `foo` transform for each applicable file by calling:

    foo(file, { x: 3, beep: true })


Many npm modules that don't do IO will just work after being browserified. Others take more work.

Many node built-in modules have been wrapped to work in the browser, but only when you explicitly require() or use their functionality.

When you require() any of these modules, you will get a browser-specific shim:

Additionally, if you use any of these variables, they will be defined in the bundled output in a browser-appropriate way:

  • process
  • Buffer
  • global - top-level scope object (window)
  • __filename - file path of the currently executing file
  • __dirname - directory path of the currently executing file

more examples

external requires

You can just as easily create a bundle that will export a require() function so you can require() modules from another script tag. Here we'll create a bundle.js with the through and duplexer modules.

$ browserify -r through -r duplexer -r ./my-file.js:my-module > bundle.js

Then in your page you can do:

<script src="bundle.js"></script>
  var through = require('through');
  var duplexer = require('duplexer');
  var myModule = require('my-module');
  /* ... */

external source maps

If you prefer the source maps be saved to a separate .js.map source map file, you may use exorcist in order to achieve that. It's as simple as:

$ browserify main.js --debug | exorcist bundle.js.map > bundle.js

Learn about additional options here.

multiple bundles

If browserify finds a required function already defined in the page scope, it will fall back to that function if it didn't find any matches in its own set of bundled modules.

In this way, you can use browserify to split up bundles among multiple pages to get the benefit of caching for shared, infrequently-changing modules, while still being able to use require(). Just use a combination of --external and --require to factor out common dependencies.

For example, if a website with 2 pages, beep.js:

var robot = require('./robot.js');

and boop.js:

var robot = require('./robot.js');

both depend on robot.js:

module.exports = function (s) { return s.toUpperCase() + '!' };
$ browserify -r ./robot.js > static/common.js
$ browserify -x ./robot.js beep.js > static/beep.js
$ browserify -x ./robot.js boop.js > static/boop.js

Then on the beep page you can have:

<script src="common.js"></script>
<script src="beep.js"></script>

while the boop page can have:

<script src="common.js"></script>
<script src="boop.js"></script>

This approach using -r and -x works fine for a small number of split assets, but there are plugins for automatically factoring out components which are described in the partitioning section of the browserify handbook.

api example

You can use the API directly too:

var browserify = require('browserify');
var b = browserify();


var browserify = require('browserify')

browserify([files] [, opts])

Returns a new browserify instance.

String, file object, or array of those types (they may be mixed) specifying entry file(s).

files and opts are both optional, but must be in the order shown if both are passed.

Entry files may be passed in files and / or opts.entries.

External requires may be specified in opts.require, accepting the same formats that the files argument does.

If an entry file is a stream, its contents will be used. You should pass opts.basedir when using streaming files so that relative requires can be resolved.

opts.entries has the same definition as files.

opts.noParse is an array which will skip all require() and global parsing for each file in the array. Use this for giant libs like jquery or threejs that don't have any requires or node-style globals but take forever to parse.

opts.transform is an array of transform functions or modules names which will transform the source code before the parsing.

opts.ignoreTransform is an array of transformations that will not be run, even if specified elsewhere.

opts.plugin is an array of plugin functions or module names to use. See the plugins section below for details.

opts.extensions is an array of optional extra extensions for the module lookup machinery to use when the extension has not been specified. By default browserify considers only .js and .json files in such cases.

opts.basedir is the directory that browserify starts bundling from for filenames that start with ..

opts.paths is an array of directories that browserify searches when looking for modules which are not referenced using relative path. Can be absolute or relative to basedir. Equivalent of setting NODE_PATH environmental variable when calling browserify command.

opts.commondir sets the algorithm used to parse out the common paths. Use false to turn this off, otherwise it uses the commondir module.

opts.fullPaths disables converting module ids into numerical indexes. This is useful for preserving the original paths that a bundle was generated with.

opts.builtins sets the list of built-ins to use, which by default is set in lib/builtins.js in this distribution.

opts.bundleExternal boolean option to set if external modules should be bundled. Defaults to true.

When opts.browserField is false, the package.json browser field will be ignored.

When opts.insertGlobals is true, always insert process, global, __filename, and __dirname without analyzing the AST for faster builds but larger output bundles. Default false.

When opts.detectGlobals is true, scan all files for process, global, __filename, and __dirname, defining as necessary. With this option npm modules are more likely to work but bundling takes longer. Default true.

When opts.ignoreMissing is true, ignore require() statements that don't resolve to anything.

When opts.debug is true, add a source map inline to the end of the bundle. This makes debugging easier because you can see all the original files if you are in a modern enough browser.

When opts.standalone is a non-empty string, a standalone module is created with that name and a umd wrapper. You can use namespaces in the standalone global export using a . in the string name as a separator, for example 'A.B.C'. The global export will be sanitized and camel cased.

Note that in standalone mode the require() calls from the original source will still be around, which may trip up AMD loaders scanning for require() calls. You can remove these calls with derequire:

$ npm install -g derequire
$ browserify main.js --standalone Foo | derequire > bundle.js

opts.insertGlobalVars will be passed to insert-module-globals as the opts.vars parameter.

opts.externalRequireName defaults to 'require' in expose mode but you can use another name.

opts.bare creates a bundle that does not include Node builtins, and does not replace global Node variables except for __dirname and __filename.

opts.node creates a bundle that runs in Node and does not use the browser versions of dependencies. Same as passing { bare: true, browserField: false }.

Note that if files do not contain javascript source code then you also need to specify a corresponding transform for them.

All other options are forwarded along to module-deps and browser-pack directly.

b.add(file, opts)

Add an entry file from file that will be executed when the bundle loads.

If file is an array, each item in file will be added as an entry file.

b.require(file, opts)

Make file available from outside the bundle with require(file).

The file param is anything that can be resolved by require.resolve(), including files from node_modules. Like with require.resolve(), you must prefix file with ./ to require a local file (not in node_modules).

file can also be a stream, but you should also use opts.basedir so that relative requires will be resolvable.

If file is an array, each item in file will be required. In file array form, you can use a string or object for each item. Object items should have a file property and the rest of the parameters will be used for the opts.

Use the expose property of opts to specify a custom dependency name. require('./vendor/angular/angular.js', {expose: 'angular'}) enables require('angular')


Bundle the files and their dependencies into a single javascript file.

Return a readable stream with the javascript file contents or optionally specify a cb(err, buf) to get the buffered results.


Prevent file from being loaded into the current bundle, instead referencing from another bundle.

If file is an array, each item in file will be externalized.

If file is another bundle, that bundle's contents will be read and excluded from the current bundle as the bundle in file gets bundled.


Prevent the module name or file at file from showing up in the output bundle.

If file is an array, each item in file will be ignored.

Instead you will get a file with module.exports = {}.


Prevent the module name or file at file from showing up in the output bundle.

If file is an array, each item in file will be excluded.

If your code tries to require() that file it will throw unless you've provided another mechanism for loading it.

b.transform(tr, opts={})

Transform source code before parsing it for require() calls with the transform function or module name tr.

If tr is a function, it will be called with tr(file) and it should return a through-stream that takes the raw file contents and produces the transformed source.

If tr is a string, it should be a module name or file path of a transform module with a signature of:

var through = require('through');
module.exports = function (file) { return through() };

You don't need to necessarily use the through module. Browserify is compatible with the newer, more verbose Transform streams built into Node v0.10.

Here's how you might compile coffee script on the fly using .transform():

var coffee = require('coffee-script');
var through = require('through');

b.transform(function (file) {
    var data = '';
    return through(write, end);

    function write (buf) { data += buf }
    function end () {

Note that on the command-line with the -c flag you can just do:

$ browserify -c 'coffee -sc' main.coffee > bundle.js

Or better still, use the coffeeify module:

$ npm install coffeeify
$ browserify -t coffeeify main.coffee > bundle.js

If opts.global is true, the transform will operate on ALL files, despite whether they exist up a level in a node_modules/ directory. Use global transforms cautiously and sparingly, since most of the time an ordinary transform will suffice. You can also not configure global transforms in a package.json like you can with ordinary transforms.

Global transforms always run after any ordinary transforms have run.

Transforms may obtain options from the command-line with subarg syntax:

$ browserify -t [ foo --bar=555 ] main.js

or from the api:

b.transform('foo', { bar: 555 })

In both cases, these options are provided as the second argument to the transform function:

module.exports = function (file, opts) { /* opts.bar === 555 */ }

Options sent to the browserify constructor are also provided under opts._flags. These browserify options are sometimes required if your transform needs to do something different when browserify is run in debug mode, for example.

b.plugin(plugin, opts)

Register a plugin with opts. Plugins can be a string module name or a function the same as transforms.

plugin(b, opts) is called with the browserify instance b.

For more information, consult the plugins section below.


There is an internal labeled-stream-splicer pipeline with these labels:

  • 'record' - save inputs to play back later on subsequent bundle() calls
  • 'deps' - module-deps
  • 'json' - adds module.exports= to the beginning of json files
  • 'unbom' - remove byte-order markers
  • 'unshebang' - remove #! labels on the first line
  • 'syntax' - check for syntax errors
  • 'sort' - sort the dependencies for deterministic bundles
  • 'dedupe' - remove duplicate source contents
  • 'label' - apply integer labels to files
  • 'emit-deps' - emit 'dep' event
  • 'debug' - apply source maps
  • 'pack' - browser-pack
  • 'wrap' - apply final wrapping, require= and a newline and semicolon

You can call b.pipeline.get() with a label name to get a handle on a stream pipeline that you can push(), unshift(), or splice() to insert your own transform streams.


Reset the pipeline back to a normal state. This function is called automatically when bundle() is called multiple times.

This function triggers a 'reset' event.


browserify uses the package.json in its module resolution algorithm, just like node. If there is a "main" field, browserify will start resolving the package at that point. If there is no "main" field, browserify will look for an "index.js" file in the module root directory. Here are some more sophisticated things you can do in the package.json:

browser field

There is a special "browser" field you can set in your package.json on a per-module basis to override file resolution for browser-specific versions of files.

For example, if you want to have a browser-specific module entry point for your "main" field you can just set the "browser" field to a string:

"browser": "./browser.js"

or you can have overrides on a per-file basis:

"browser": {
  "fs": "level-fs",
  "./lib/ops.js": "./browser/opts.js"

Note that the browser field only applies to files in the local module, and like transforms, it doesn't apply into node_modules directories.


You can specify source transforms in the package.json in the browserify.transform field. There is more information about how source transforms work in package.json on the module-deps readme.

For example, if your module requires brfs, you can add

"browserify": { "transform": [ "brfs" ] }

to your package.json. Now when somebody require()s your module, brfs will automatically be applied to the files in your module without explicit intervention by the person using your module. Make sure to add transforms to your package.json dependencies field.


b.on('file', function (file, id, parent) {})

b.pipeline.on('file', function (file, id, parent) {})

When a file is resolved for the bundle, the bundle emits a 'file' event with the full file path, the id string passed to require(), and the parent object used by browser-resolve.

You could use the file event to implement a file watcher to regenerate bundles when files change.

b.on('package', function (pkg) {})

b.pipeline.on('package', function (pkg) {})

When a package file is read, this event fires with the contents. The package directory is available at pkg.__dirname.

b.on('bundle', function (bundle) {})

When .bundle() is called, this event fires with the bundle output stream.

b.on('reset', function () {})

When the .reset() method is called or implicitly called by another call to .bundle(), this event fires.

b.on('transform', function (tr, file) {})

b.pipeline.on('transform', function (tr, file) {})

When a transform is applied to a file, the 'transform' event fires on the bundle stream with the transform stream tr and the file that the transform is being applied to.


For some more advanced use-cases, a transform is not sufficiently extensible. Plugins are modules that take the bundle instance as their first parameter and an option hash as their second.

Plugins can be used to do perform some fancy features that transforms can't do. For example, factor-bundle is a plugin that can factor out common dependencies from multiple entry-points into a common bundle. Use plugins with -p and pass options to plugins with subarg syntax:

browserify x.js y.js -p [ factor-bundle -o bundle/x.js -o bundle/y.js ] \
  > bundle/common.js

For a list of plugins, consult the browserify-plugin tag on npm.

list of source transforms

There is a wiki page that lists the known browserify transforms.

If you write a transform, make sure to add your transform to that wiki page and add a package.json keyword of browserify-transform so that people can browse for all the browserify transforms on npmjs.org.

third-party tools

There is a wiki page that lists the known browserify tools.

If you write a tool, make sure to add it to that wiki page and add a package.json keyword of browserify-tool so that people can browse for all the browserify tools on npmjs.org.


Releases are documented in changelog.markdown and on the browserify twitter feed.




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