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JS Beautifier

...or, more specifically, all of the code powering

This little beautifier will reformat and reindent bookmarklets, ugly JavaScript, unpack scripts packed by Dean Edward’s popular packer, as well as deobfuscate scripts processed by


To beautify from the command-line you can use the provided Python script/library or npm package.


./js-beautify file.js beautifies a file, output goes to stdout.

To use jsbeautifier as a library is simple:

import jsbeautifier
res = jsbeautifier.beautify('your javascript string')
res = jsbeautifier.beautify_file('some_file.js')

...or, to specify some options:

opts = jsbeautifier.default_options()
opts.indent_size = 2
res = jsbeautifier.beautify('some javascript', opts)


As an alternative to the Python script, you may install the NPM package js-beautify. When installed globally, it provides an executable js-beautify script. As with the Python script, the beautified result is sent to stdout unless otherwise configured.

$ npm -g install js-beautify
$ js-beautify foo.js

You can also use js-beautify as a node library (install locally, the npm default):

$ npm install js-beautify
var beautify = require('js-beautify').js_beautify,
    fs = require('fs');

fs.readFile('foo.js', 'utf8', function (err, data) {
    if (err) {
        throw err;
    console.log(beautify(data, { indent_size: 2 }));


These are the command-line flags for both Python and JS scripts:

CLI Options:
  -f, --file                    Input file(s) (Pass '-' for stdin). These can also be passed directly.
  -r, --replace                 Write output in-place, replacing input
  -o, --outfile                 Write output to file (default stdout)
  --config                      Path to config file
  --type                        [js|css|html] ["js"]
  -q, --quiet                   Suppress logging to stdout
  -v, --version                 Show the version
  -h, --help                    Show this help

Beautifier Options:
  -s, --indent-size             Indentation size [4]
  -c, --indent-char             Indentation character [" "]
  -l, --indent-level            Initial indentation level [0]
  -t, --indent-with-tabs        Indent with tabs, overrides -s and -c
  -p, --preserve-newlines       Preserve existing line-breaks (--no-preserve-newlines disables)
  -m, --max-preserve-newlines   Maximum number of line-breaks to be preserved in one chunk [10]
  -j, --jslint-happy            Enable jslint-stricter mode
  -b, --brace-style             [collapse|expand|end-expand|expand-strict] ["collapse"]
  -B, --break-chained-methods   Break chained method calls across subsequent lines
  -k, --keep-array-indentation  Preserve array indentation
  -x, --unescape-strings        Decode printable characters encoded in xNN notation
  -w, --wrap-line-length        Wrap lines at next opportunity after N characters [0]
  --good-stuff                  Warm the cockles of Crockford's heart

These largely correspond to the underscored option keys for both library interfaces, which have these defaults:

    "indent_size": 4,
    "indent_char": " ",
    "indent_level": 0,
    "indent_with_tabs": false,
    "preserve_newlines": true,
    "max_preserve_newlines": 10,
    "jslint_happy": false,
    "brace_style": "collapse",
    "keep_array_indentation": false,
    "keep_function_indentation": false,
    "space_before_conditional": true,
    "break_chained_methods": false,
    "eval_code": false,
    "unescape_strings": false,
    "wrap_line_length": 0

In addition to CLI arguments, you may pass config to the JS executable via:

  • any jsbeautify_-prefixed environment variables
  • a JSON-formatted file indicated by the --config parameter
  • a .jsbeautifyrc file containing JSON data at any level of the filesystem above $PWD

Configuration sources provided earlier in this stack will override later ones.

You might notice that the CLI options and defaults hash aren't 100% correlated. Historically, the Python and JS APIs have not been 100% identical. For example, space_before_conditional is currently JS-only, and not addressable from the CLI script. There are a few other additional cases keeping us from 100% API-compatibility. Patches welcome!


In addition to the js-beautify executable, css-beautify and html-beautify are also provided as an easy interface into those scripts. Alternatively, js-beautify --css or js-beautify --html will accomplish the same thing, respectively.

// Programmatic access
var beautify_js = require('js-beautify'); // also available under "js" export
var beautify_css = require('js-beautify').css;
var beautify_html = require('js-beautify').html;

// All methods accept two arguments, the string to be beautified, and an options object.

The CSS & HTML beautifiers are much simpler in scope, and possess far fewer options.

CSS Beautifier Options:
  -s, --indent-size             Indentation size [4]
  -c, --indent-char             Indentation character [" "]

HTML Beautifier Options:
  -s, --indent-size             Indentation size [4]
  -c, --indent-char             Indentation character [" "]
  -b, --brace-style             [collapse|expand|end-expand] ["collapse"]
  -S, --indent-scripts          [keep|separate|normal] ["normal"]
  -W, --max-char                Maximum characters per line (0 disables) [250]
  -U, --unformatted             List of tags (defaults to inline) that should not be reformatted


You are free to use this in any way you want, in case you find this useful or working for you. (MIT)


Written by Einar Lielmanis, Python version flourished by Stefano Sanfilippo

Thanks to Jason Diamond, Patrick Hof, Nochum Sossonko, Andreas Schneider, Dave Vasilevsky, Vital Batmanov, Ron Baldwin, Gabriel Harrison, Chris J. Shull, Mathias Bynens, Vittorio Gambaletta and others.

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