Automattic/juice

Juice

Given HTML, Juice will inline your CSS properties into the style attribute.

Some projects using Juice →

How to use

Juice has a number of functions based on whether you want to process a file, HTML string, or a cheerio document, and whether you want Juice to automatically get remote stylesheets, scripts and image dataURIs to inline.

To inline HTML without getting remote resources, using default options:

import juice from 'juice';

const result = juice("<style>div{color:red;}</style><div/>");

result will be:

<div style="color: red;"></div>

Try out the web client version

What is this useful for?

• HTML emails. For CSS support in email clients see Can I Email.
• Embedding HTML in 3rd-party websites.

Documentation

Juice is exposed as a standard module, and from CLI with a smaller set of options.

Modern CSS support

Juice handles modern CSS out of the box: nested rules (CSS Nesting Module Level 1, .card { &:hover { ... } }) are flattened automatically before inlining, @container and @layer at-rules pass through verbatim, and specificity for :is() / :where() / :has() / :not() is computed per the CSS Selectors Level 4 spec.

Options

All Juice methods take an options object that can contain any of these properties, though not every method uses all of these:

Methods

juice(html [, options])

Returns a string containing the HTML with inlined CSS.

Does not fetch remote resources.

• html - HTML string, accepts complete documents as well as fragments
• options - optional, see Options above

juice.juiceResources(html, options, callback)

Callback returns a string containing the HTML with inlined CSS.

Fetches remote resources.

• html - (string) HTML
• options - see Options above
• callback(err, html)
  • err - Error object or null
  • html - (string) HTML with inlined CSS

juice.juiceFile(filePath, options, callback)

Callback returns a string containing the HTML with inlined CSS.

Fetches remote resources.

• filePath - path to the HTML file to be Juiced
• options - see Options above
• callback(err, html)
  • err - Error object or null
  • html - (string) HTML with inlined CSS

juice.juiceDocument($ [, options])

This takes a cheerio instance and performs inlining in-place. Returns the same cheerio instance. Does not fetch remote resources.

• $ - a cheerio instance, be sure to use the same cheerio version that Juice uses
• options - (object) optional, see Options above

juice.inlineContent(html, css [, options])

This takes HTML and CSS and returns new HTML with the provided CSS inlined.

It does not look at <style> or <link rel="stylesheet"> elements at all.

• html - HTML string
• css - CSS string
• options - (object) optional, see Options above

juice.inlineDocument($, css [, options])

Given a cheerio instance and CSS, this modifies the cheerio instance so that the provided CSS is inlined. It does not look at <style> or <link rel="stylesheet"> elements at all.

• $ - a cheerio instance, be sure to use the same cheerio version that juice uses
• css - CSS string
• options - (object) optional, see Options above

Global settings

juice.codeBlocks

Type: Object
Default:

{
  EJS: { start: '<%', end: '%>' },
  HBS: { start: '{{', end: '}}' }
}

An object where each value has a start and end to specify fenced code blocks that should be ignored during parsing and inlining.

For example, Handlebars (hbs) templates are juice.codeBlocks.HBS = {start: '{{', end: '}}'}. codeBlocks can fix problems where otherwise juice might interpret code like <= as HTML, when it is meant to be template language code.

Note that codeBlocks is a dictionary which can contain many different code blocks, so don't do juice.codeBlocks = {...} do juice.codeBlocks.myBlock = {...}

juice.ignoredPseudos

Type: Array
Default: ['hover', 'active', 'focus', 'visited', 'link']

Array of ignored pseudo-selectors such as 'hover' and 'active'.

juice.widthElements

Type: Array
Default: ['TABLE', 'TD', 'TH', 'IMG']

Array of HTML elements that can receive width attributes.

juice.heightElements

Type: Array
Default: ['TABLE', 'TD', 'TH', 'IMG']

Array of HTML elements that can receive height attributes.

juice.styleToAttribute

Type: Object
Default:

{
  'background-color': 'bgcolor',
  'background-image': 'background',
  'text-align': 'align',
  'vertical-align': 'valign'
}

Object of style property names (key) to their respective attribute names (value).

juice.tableElements

Type: Array
Default: ['TABLE', 'TH', 'TR', 'TD', 'CAPTION', 'COLGROUP', 'COL', 'THEAD', 'TBODY', 'TFOOT']

Array of table HTML elements that can receive attributes defined in juice.styleToAttribute.

juice.nonVisualElements

Type: Array
Default: [ 'HEAD', 'TITLE', 'BASE', 'LINK', 'STYLE', 'META', 'SCRIPT', 'NOSCRIPT' ]

Array of elements that will not have styles inlined because they are not intended to render.

juiceClient.excludedProperties

Type: Array
Default: []

Array of CSS properties that won't be inlined.

Special markup

data-embed

Add data-embed to any <style> tag to prevent Juice from inlining its CSS and removing it. Can be used to embed email client support hacks that rely on CSS selectors into your email templates:

<style data-embed>
  u + .body .your-class-name {
    /* CSS here targets Gmail */
  }
</style>

The data-embed attribute will be removed from the output HTML, but no inlining or style tag removal will take place:

<style>
  u + .body .your-class-name {
    /* CSS here targets Gmail */
  }
</style>

data-juice-duplicates

Override the inlineDuplicateProperties option for a single element by adding data-juice-duplicates to it. The attribute presence (or data-juice-duplicates="true") enables duplicate declarations for that element; data-juice-duplicates="false" disables them:

<!-- keeps both background-color declarations, even if the option is off -->
<div class="header" data-juice-duplicates></div>

<!-- collapses to the highest-specificity declaration, even if the option is on -->
<div class="header" data-juice-duplicates="false"></div>

The data-juice-duplicates attribute is removed from the output HTML.

data-juice-important

Override the preserveImportant option for a single element by adding data-juice-important to it. The attribute presence (or data-juice-important="true") preserves !important in that element's inlined declarations; data-juice-important="false" strips it:

<!-- keeps !important in the inlined style, even if the option is off -->
<div class="cta" data-juice-important></div>

<!-- strips !important from the inlined style, even if the option is on -->
<div class="cta" data-juice-important="false"></div>

The data-juice-important attribute is removed from the output HTML.

Ignoring CSS with comments

You can use special CSS comments to prevent Juice from inlining entire CSS files, rules, or even just declarations.

Ignore entire file

Add a /* juice ignore */ comment on the first line in your CSS:

<style>
  /* juice ignore */
  body { color: red; }
  .test { color: blue; }
</style>

<body>
  <div class="test">Hello World</div>
</body>

The entire CSS will be ignored (as in, not inlined).

With removeStyleTags: true, the whole <style> tag will be preserved.

Ignore next rule

Add /* juice ignore next */ before any CSS rule to skip inlining that rule:

body { color: black; }

/* juice ignore next */
h1 {
  color: blue;
}

p { color: green; }

The h1 rule will not be inlined, but will be preserved when removeStyleTags: true. The body and p rules will be inlined normally.

Ignore next declaration

Add /* juice ignore next */ inside a CSS rule to skip inlining the next declaration:

.test {
  color: red;
  /* juice ignore next */
  font-weight: bold;
  font-size: 14px;
}

The color and font-size will be inlined, but font-weight will not. The rule with the ignored declaration will be preserved in a <style> tag when removeStyleTags: true.

Ignore blocks of code

Use start/end comment pairs to ignore multiple rules:

h1 {
  color: black;
}

/* juice start ignore */
h2 {
  color: pink;
}

h3 {
  color: lightcoral;
}
/* juice end ignore */

h4 {
  color: green;
}

The h2 and h3 rules will not be inlined but will be preserved in a <style> tag when removeStyleTags: true. The h1 and h4 rules will be inlined normally.

CLI Options

To use Juice from CLI, run juice [options] input.html output.html

For a listing of all available options, just type juice -h.

Note that if you want to just type juice from the command line, you should npm install juice -g so it is globally available.

The CLI should have all the above options with the names changed from camel case to hyphen-delimited, so for example extraCss becomes extra-css and webResources.scripts becomes web-resources-scripts.

These are additional options not included in the standard juice options listed above:

• --css [filepath] will load and inject CSS into extraCss.
• --options-file [filepath] will load and inject options from a JSON file. Options from the CLI will be given priority over options in the file when there is a conflict.
• codeBlocks is optionally supported in the options file if you include it. This will allow you to support different template languages in a build process.

Running Juice in the Browser

Juice's default entry imports Node-only modules (fs, path), so it cannot run as-is in the browser. For browser builds, import juice/client instead, which exposes juiceDocument, inlineDocument, and inlineContent (but not juiceFile, juiceResources, or inlineExternal).

Juice is ESM-only as of v12. Any modern bundler — Vite, webpack 5, esbuild, Rollup, Parcel 2+ — will pick up juice/client correctly via the "browser" field in package.json. Browserify is not supported on v12+ (it can't parse ESM). Note that automated tests are not running in the browser yet.

License

MIT Licensed, see LICENSE.md.

3rd-party

• Uses cheerio for the underlying DOM representation.
• Uses mensch to parse out CSS and Slick to tokenize them.
• Icon by UnheardSounds