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Inline CSS

Automatically inline CSS from <style> tags in your HTML emails. CSS inlining is still important in HTML email, mainly because of Outlook on Windows, which doesn’t support multiple classes on elements. It can also help preserve a decent layout in email clients that do not support embedded CSS (in <style> tags), or when an email is forwarded. The utility-first approach in Tailwind CSS works great with CSS inlining: utility classes are not ‘global’, so you won’t end up with a font-family inlined on every element (unless you really, really want to).

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Usage

To enable CSS inlining, simply set css.inline to true in your config:
config.js
export default {
  css: {
    inline: true,
  }
}
You will want to keep CSS inlining off when developing AMP4EMAIL templates

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Customization

If you need control over how your CSS is inlined, you may pass a configuration object to inlineCSS. Doing this in your Environment config.js will enable CSS inlining for all Templates when building for that Environment.

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styleToAttribute

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styleToAttribute
Object
default:"{}"
Defines which CSS properties should be duplicated as what HTML attributes.
For example, this property-attribute assignment:
config.js
export default {
  css: {
    inline: {
      styleToAttribute: {
        'background-color': 'bgcolor',
      }
    }
  }
}
… will transform this: 
<table class="bg-slate-300">
  <tr>
    <td>...</td>
  </tr>
</table>
… into this: 
<table bgcolor="#cbd5e1" style="background-color: #cbd5e1">
  <tr>
    <td>...</td>
  </tr>
</table>
The available mappings are:
CSS PropertyHTML Attribute
background-colorbgcolor
background-imagebackground
text-alignalign
vertical-alignvalign

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attributeToStyle

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attributeToStyle
Boolean|String[]
default:"undefined"
Duplicates specified HTML attributes as inline CSS.
See the documentation here.

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applyWidthAttributes

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applyWidthAttributes
Boolean
default:"true"
Whether to use any CSS pixel widths to create width attributes on elements set in css.inline.widthElements.
Set it to false to prevent any width attributes from being added based on inline CSS width:
config.js
export default {
  css: {
    inline: {
      applyWidthAttributes: false,
    }
  }
}

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widthElements

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widthElements
String[]
default:"['img', 'video']"
Array of HTML elements that can receive width attributes based on inline CSS width.
config.js
export default {
  css: {
    inline: {
      widthElements: ['table', 'td', 'th'],
    }
  }
}

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applyHeightAttributes

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applyHeightAttributes
Boolean
default:"true"
Whether to use any CSS pixel heights to create height attributes on elements set in css.inline.heightElements.
Set it to false to prevent any height attributes from being added based on inline CSS height:
config.js
export default {
  css: {
    inline: {
      applyHeightAttributes: false,
    }
  }
}

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heightElements

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heightElements
String[]
default:"['img', 'video']"
Array of HTML elements that can receive height attributes based on inline CSS height.
config.js
export default {
  css: {
    inline: {
      heightElements: ['table', 'td', 'th'],
    }
  }
}

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excludedProperties

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excludedProperties
String[]
default:"[]"
Array of CSS property names that should be excluded from the CSS inlining process.
Names are considered unique, so you will need to specify each one you’d like to exclude. For example:
config.js
export default {
  css: {
    inline: {
      excludedProperties: ['padding', 'padding-left'],
    }
  }
}
--tw-shadow is automatically excluded from the properties that can be inlined.

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codeBlocks

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codeBlocks
Object
default:"{ EJS: {}, HBS: {} }"
An object where each value has a start and end to specify fenced code blocks that should be ignored during CSS inlining.
By default, EJS and HBS code blocks are ignored: 
{
  EJS: { start: '<%', end: '%>' },
  HBS: { start: '{{', end: '}}' },
}

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removeInlinedSelectors

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removeInlinedSelectors
Boolean
default:"true"
When css.inline is enabled, classes will be removed from the class attribute of a tag after they have been successfully inlined.
Set this option to false to preserve the classes in the class attribute.
config.production.js
export default {
  css: {
    inline: {
      removeInlinedSelectors: false,
    }
  }
}

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preferUnitlessValues

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preferUnitlessValues
Boolean
default:"true"
When inlining CSS, 0 values will be inlined without units.
For example, margin: 0px will be inlined as margin: 0. Set this to false to keep units on 0 values.
config.js
export default {
  css: {
    inline: {
      preferUnitlessValues: false,
    }
  }
}

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useAttributeSizes

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useAttributeSizes
Boolean
default:"undefined"
Prefer HTML width and height attributes over inline CSS.
Useful for retina images in Outlook on Windows, which doesn’t respect CSS sizes and will render the image in its natural size. Set this to true to use HTML attributes for sizes instead of inline CSS:
config.js
export default {
  css: {
    inline: {
      useAttributeSizes: true,
    }
  }
}
useAttributeSizes will apply to all elements defined in widthElements and heightElements

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safelist

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safelist
String[]
An array of strings representing CSS selectors that should not be removed after inlining.
These can be substring matches, so you can use text-red to preserve .text-red, .text-red-500, etc.
config.js
export default {
  css: {
    inline: {
      safelist: ['text-red', '.bg-blue-500'],
    }
  }
}

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Prevent inlining

You may add an attribute on a <style> tag to prevent Juice from inlining the CSS inside it. Useful for writing email client CSS hacks, or for preserving CSS comments when using the removeCSSComments: false Cleanup option. 
<style data-embed>
  /* This CSS will not be inlined */
  .text-red { color: red; }
</style>
Maizzle supports the following attributes for this purpose:
  • data-embed
  • no-inline
  • embed
CSS selectors that don’t appear in your markup will still need to be whitelisted for purging.

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API

You can use the inlineCSS function to inline CSS in a string of HTML. Your HTML string will need to have at least one <style> tag in the <head>. Alternatively, you may pass your own CSS to inline through the customCSS option. Additionally, you may configure the Juice library by passing options in the same object.
app.js
import { inlineCSS } from '@maizzle/framework'

const config = {
  customCSS: 'body { background-color: #f8f9fa; }',
  excludedProperties: ['padding', 'padding-left'] // Juice option
}

const html = await inlineCSS('html string', config)

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