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Jekyll Assets

Jekyll Assets is a drop in asset pipeline that uses Sprockets to build specifically for Jekyll. It utilizes Sprockets, and Jekyll to try and achieve a clean, and extensible assets platform that supports plugins, caching, converting your assets. It even supports proxying of said assets in a way that does not interfere with either Sprockets, or Jekyll, or your own source. By default you can add Jekyll Assets to your Gemfile, as a plugin, and have it act as a drop-in replacement for Jekyll's basic SASS processors, with you only having to add it to your Gemfile, and updating your <img>, and <link>.


gem "jekyll-assets", group: :jekyll_plugins
gem "jekyll-assets", git: "", group: :jekyll_plugins
gem "jekyll-assets", "~> x.x.alpha", group: :jekyll_plugins

System Requirements

  • ruby: 2.3+
  • sprockets: 3.3+
  • jekyll: 3.5+

If you'd like SourceMaps, or faster Sprockets, opt to use Sprockets 4.0, you can use it by placing it to your Gemfile.

gem "sprockets", "~> 4.0.beta", {
  require: false


The configuration file is the same as Jekyll's, which is _config.yml. Except we use the special key called assets inside of that file. All values listed below are default, you need not copy these into your configuration file unless you plan to change a value. Setting a value makes it explicit, and shared across both **production, and **development.

source_maps: true # false on JEKYLL_ENV=production
destination: "/assets"
compression: true
gzip: false
   js: { integrity: false } # true on JEKYLL_ENV=production
  css: { integrity: false } # true on JEKYLL_ENV=production
  img: { integrity: false } # true on JEKYLL_ENV=production
  path: ".jekyll-cache/assets"
  type: file # Possible values: memory, file
  enabled: true
# --
# Assets you wish to always have compiled.
#   This can also be combined with raw_precompile which
#   copies assets without running through the pipeline
#   making them ultra fast.
# --
precompile: []
raw_precompile: [
# --
# baseurl: whether or not to append site.baseurl
# destination: the folder you store them in on the CDN.
# url: the CDN url (fqdn, or w/ identifier).
# --
  baseurl: false
  destination: false
  url: null
# --
# These are all default. No need to add them
#   Only use this if you have more.
# --
  - assets/css
  - assets/fonts
  - assets/images
  - assets/videos
  - assets/javascript
  - assets/video
  - assets/image
  - assets/img
  - assets/js
  - _assets/css
  - _assets/fonts
  - _assets/images
  - _assets/videos
  - _assets/javascript
  - _assets/video
  - _assets/image
  - _assets/img
  - _assets/js
  - css
  - fonts
  - images
  - videos
  - javascript
  - video
  - image
  - img
  - js
  css: { autoprefixer: {}}
  img: { optim: {}}

Tag {% asset %}, <img>

{% asset src @magick:2x alt='This is my alt' %}
{% asset src @magick:2x alt='This is my alt' %}
<img src="src" asset="@magick:2x" alt="This is my alt">
<img src="src" alt="This is my alt" asset>


We provide several defaults that get set when you run an asset, depending on content type, this could be anything from type, all the way to integrity. If there is a default attribute you do not wish to be included, you can disable the attribute with !attribute, and it will be skipped over.

{% asset img.png !integrity %}
{% asset bundle.css !type   %}


Our tags will take any number of arguments, and convert them to HTML, and even attach them to your output if the HTML processor you use accepts that kind of data. This applies to anything but hashes, and arrays. So adding say, a class, or id, is as easy as doing id="val" inside of your tag arguments.

Built In

Arg Description Type Return Type
@path Path */* text
@data data URI */* text
@inline CSS <style> text/css text/html
text/svg+xml XML image/svg+xml text/svg+xml
JavaScript <script> application/javascript text/html
Image <img> image/* text/html
srcset Responsive <img> image/* text/html
srcset + @pic Responsive <pic> image/* text/html

Jekyll Assets uses @envygeeks liquid-tag-parser which supports advanced arguments (hash based arguments) as well as array based arguments. When you see something like k1:sk1=val it will get converted to k1 = { sk1: "val" } in Ruby. To find out more about how we process tags you should visit the documentation for liquid-tag-parser

Responsive Images

Jekyll Assets has the concept of responsive images, using the picture (when using @pic w/ srcset) and the <img> tag when using srcset. If you ship multiple srcset with your image, we will proxy, build and then ship out a picture/img tag with any number of source/srcset, and in the case of picture, with the original image being the image.

<picture> usage, requires @pic
{% asset img.png @pic
    srcset:max-width="200 2x"
    srcset:max-width="150 1.5x"
    srcset:max-width="100 1x"
  <source srcset="1.png 2x"   media="(max-width:200px)">
  <source srcset="2.png 1.5x" media="(max-width:150px)">
  <source srcset="3.png 1x"   media="(max-width:100px)">
  <img src="img.png">
<img> usage
{% asset img.png
    srcset:width="200 2x"
    srcset:width="150 1.5x"
    srcset:width="100 1x"

{% asset img.svg
    srcset:width="200 2x jpg"
    srcset:width="150 1.5x jpg"
    srcset:width="100 1x jpg"

{% asset img.png
<img srcset="1.png 2x, 2.png 1.5x, 3.png 1x">
<img srcset="1.jpg 2x, 2.jpg 1.5x, 3.jpg 1x">
<img srcset="1.png 200w, 2.png 150w, 3.pnx 200w">
Args for <img srcset>
Arg Type Description
width Width [Density, Type] Resize, set srcset="<Src> <<Width>px/Density>"
Args for @pic
Arg Type Description
min-width Width [Density] Resize, set media="(min-width: <Width>px)"
max-width Width [Density] Resize, set media="(max-width: <Width>px)"
sizes Any Your value, unaltered, unparsed.
media Any Your value, unaltered, unparsed.

If you set media, w/ max-width, min-width, we will not ship media, we will simply resize and assume you know what you're doing. Our parser is not complex, and does not make a whole lot of assumptions on your behalf, it's simple and only meant to make your life easier. In the future we may make it more advanced.


We support liquid arguments for tag values (but not tag keys), and we also support Liquid pre-processing (with your Jekyll context) of most files if they end with .liquid. This will also give you access to our filters as well as their filters, and Jekyll's filters, and any tags that are globally available.

{% asset '{{ site.bg_img }}' %}
{% asset '{{ site.bg_img }}' proxy:key='{{ value }}' %}
{% asset {{\ site.bg_img\ }} %}

.sass, .scss

body {
  background-image: asset_url("'{{ site.bg_img }}'");
  background-image: asset_url("'{{ site.bg_img }}' proxy:key='{{ value }}'");
  background-image: asset_url("{{\ site.bg_img\ }}");



.bg {
  background: url(asset_path("{{ site.background_image }}"));

You have full access to your entire global context from any liquid processing we do. Depending on where you do it, you might or might not also have access to your local (page) context as well. You can also do whatever you like, and be as dynamic as you like, including full loops, and conditional Liquid, since we pre-process your text files. On Sprockets 4.x you can use .liquid.ext and .ext.liquid, but because of the way Sprockets 3.x works, we have opted to only allow the default extension of .ext.liquid when running on "Old Sprockets" (AKA 3.x.) If you would like Syntax + Liquid you should opt to install Sprockets 4.x so you can get the more advanced features.


In order to import your Liquid pre-processed assets inside of Liquid or JS you should use a Sprockets //require=, Sprockets does not integrate that deeply into JavaScript and SASS to allow you to @import and pre-process.

.sass, .scss Helpers

We provide two base helpers, asset_path to return the path of an asset, and asset_url which will wrap asset_path into a url() for you, making it easy for you to extract your assets and their paths inside of SCSS. All other helpers that Sprockets themselves provide will use our asset_path helper, so you can use them like normal, including with Liquid

body {
  background-image: asset_url("img.png");

Proxies, and Other Arguments

Any argument that is supported by our regular tags, is also supported by our .sass/.scss helpers, with a few obvious exceptions (like srcset). This means that you can wrap your assets into magick if you wish, or imageoptim or any other proxy that is able to spit out a path for you to use. The general rule is, that if it returns a path, or @data then it's safe to use within .scss/.sass, otherwise it will probably throw.

body {
  background-image: asset_url("img.png @magick:half")

Note: we do not validate your arguments, so if you send a conflicting argument that results in invalid CSS, you are responsible for that, in that if you ship us srcset we might or might not throw, depending on how the threads are ran. So it might ship HTML if you do it wrong, and it will break your CSS, this is by design so that if possible, in the future, we can allow more flexibility, or so that plugins can change based on arguments.


We provide all your assets as a hash of Liquid Drops so you can get basic info that we wish you to have access to without having to prepare the class. Note: The keys in the assets array are the names of the original files, e.g., use *.scss instead of *.css.

{{ assets["bundle.css"].content_type }} => "text/css"
{{ assets["images.jpg"].width  }} => 62
{{ assets["images.jpg"].height }} => 62

The current list of available accessors:

Method Description
content_type The RFC content type
height The asset height (if available)
filename The full path to the assets actual file
width The asset width (if available)
digest_path The prefixed path
integrity The SRI hash (currently sha256)


{% for k,v in assets %}
  {{ k }}
{% endfor %}


Using Liquid Drop assets, you can check whether an asset is present.

{% if assets[page.image] %}{% img '{{ page.image }}' %}
{% else %}
  {% img default.jpg %}
{% endif %}


{{ src | asset:"@magick:2x magick:quality=92" }}

Polymer WebComponents

We have basic support for WebComponents when using Sprockets ~> 4.0.0.beta, this will allow you to place your HTML in the _assets/components folder, {% asset myComponent.html %}, and get an import, you can place your regular JS files inside of the normal structure.



<!DOCTYPE html>
    {% asset webcomponents.js %}
    {% asset test.html %}
    <contact-card starred>
      {% asset profile.jpg %}
      <span>Your Name</span>


<dom-module id="contact-card">
    <style>/* ... */</style>
    <iron-icon icon="star" hidden$="{{!starred}}"></iron-icon>
    class ContactCard extends Polymer.Element {
      static get is() { return "contact-card"; }
      static get properties() {
        return {
          starred: { type: Boolean, value: false }
    customElements.define(, ContactCard);


Point Name Instance Args
:env :before_init
:env :after_init
:env :after_write
:config :before_merge Config{}
:asset :before_compile Asset, Manifest
:asset :after_compression input{}, output{}, type=/


Jekyll::Assets::Hook.register :env, :before_init do
  append_path "myPluginsCustomPath"
Jekyll::Assets::Hook.register :config, :init do |c|
    plugins: {
      my_plugin: {
        opt: true

Plugin Hooks

Your plugin can also register it's own hooks on our Hook system, so that you can trigger hooks around your stuff as well, this is useful for extensive plugins that want more power.

Jekyll::Assets::Hook.add_point(:plugin, :hook)
Jekyll::Assets::Hook.trigger(:plugin, :hook)  { |v| }
Jekyll::Assets::Hook.trigger(:plugin, :hook) do |v|

Default Plugins

Google Closure Alternates

gem "crass"

Once crass is added, we will detect vendor prefixes, and add /* @alternate */ to them, with or without compression enabled, and with protections against compression stripping.

Font Awesome

gem "font-awesome-sass"
@import "font-awesome-sprockets";
@import "font-awesome";
html {
  // ...

CSS Auto-Prefixing

gem "autoprefixer-rails"
    - "last 2 versions"
    - "IE > 9"


gem "boostrap-sass" # 3.x
gem "bootstrap"     # 4.x
@import 'bootstrap'
html {
  // ...
//=require _bootstrap.css
//=require bootstrap/_reboot.css


gem "mini_magick"


See the MiniMagick docs to get an idea what <value> can be.

Name Accepts Value

* magick:format requires an ext or a valid MIME content type like image/jpeg or .jpg. We will ImageMagick -format on your behalf with that information by getting the extension.


gem "image_optim"
gem "image_optim_bin" # Optional



Check the ImageOptim to get idea about configuration options, and to get a list of stuff you need to install on your system to use it, if you do not wish to use "image_optim_bin",


Name Accepts Value

By default @optim will use the default jekyll, otherwise you can provide optim=preset and have it used that preset. ImageOptim provides advanced, and default as their default presets, you can define your own preset via Jekyll Assets configuration listed above.

Building Your Own Plugins


Name Class
@env Jekyll::Assets::Env
@args Liquid::Tag::Parser{}
@jekyll Jekyll::Site
@asset Sprockets::Asset


Name Class Type
@doc Nokogiri:: XML::Document image/svg+xml
@doc Nokogiri::HTML::Document image/*

Migrating from Earlier Versions








{% css css.css %}
{% img image.jpg width:60 class:image %}
{% js js.js %}


{% asset css.css %}
{% asset image.jpg width=60 class=image %}
{% asset js.js %}

Custom Tags


<link rel="apple-touch-icon-precomposed" href="{% asset_path icon.png %}">
<link rel="apple-touch-icon-precomposed" href="{% asset_data icon.png %}">


<link rel="apple-touch-icon-precomposed" href="{% asset icon.png @path %}">
<link rel="apple-touch-icon-precomposed" href="{% asset icon.png @data %}">