Easy responsive images on Github Pages with Cloudinary

⚠️ Brief Note For Perfection Seekers ⚠️

This is definitely not the best™ way to handle images. In an ideal world you would want the URLs generated off of the width and height of the images. You cannot do that in a plain-jane include though. You must reach for a custom Jekyll plugin which then makes it incompatible with the default Github Pages set of plugins.

If you are looking for the optimal solution, I would look at one of these custom plugins:

A key component to keeping your site performant is proper management of images. There are many complexities with the management of images on your website but the big goals are:

  • Serve the proper size image for your visitors device (i.e., small images for mobile, high-res images for high-res desktop devices)
  • Serve the most modern image format possible (i.e., serve webp first and then fallback to jpeg)
  • Serve the image only when necessary (i.e., if the image isn’t in the viewport, don’t waste network bandwidth loading it)

I wanted to solve these three problems keeping in mind the following three goals:

  • I didn’t want to slow down my site build time
  • I didn’t want to use extra storage by creating image formats that may never get used
  • I didn’t want to go through the process of setting up Jekyll + Github Pages w/ custom plugins (like this)
  • I wanted to spend exactly $0

Cloudinary made this so easy.

They provide a fetch method where you can just simply build a url and they will handle the rest. Here’s a sample snippet they provide:

    https://res.cloudinary.com/<cloud_name>/image/fetch/c_limit,w_320,q_auto,f_auto/https://<your-domain>/assets/img.jpg 320w,
    https://res.cloudinary.com/<cloud_name>/image/fetch/c_limit,w_640,q_auto,f_auto/https://<your-domain>/assets/img.jpg 640w
    https://res.cloudinary.com/<cloud_name>/image/fetch/c_limit,w_960,q_auto,f_auto/https://<your-domain>/assets/img.jpg 960w
    https://res.cloudinary.com/<cloud_name>/image/fetch/c_limit,w_1280,q_auto,f_auto/https://<your-domain>/assets/img.jpg 1280w
    https://res.cloudinary.com/<cloud_name>/image/fetch/c_limit,w_1600,q_auto,f_auto/https://<your-domain>/assets/img.jpg 1600w
  sizes="(min-width: 50rem) 50rem, 90vw"

Let’s break down one of those URLs here:

  • <cloud_name> - This is a name granted to you when you create a free account
  • /image/fetch - This specifies that cloudinary will be fetching the image for you from a URL you specify
  • c_limit - If the asset is larger than the desired width it will shrink it to fit maintaining the original aspect ratio
  • w_800 - Specifies I want the image to be resized to a width of 800px
  • q_auto - Specifies I want the quality to be automatically managed by cloudinary
  • f_auto - Specifies I want the format of the image served to be automatically the best image format supported by the client browser
  • https://<your-domain>/assets/img.jpg - Just a sample URL, telling cloudinary where the asset should be fetched from

The full range of transformation options you can specify in the URL is pretty impressive. Check out the docs here.

Using that HTML as a template I can write a little Jekyll liquid snippet:

{% if site.url contains "localhost" %}
<img src="{{ site.url }}{{ include.path }}" loading="{{ include.loading | default: "lazy" }}" />
{% else %}
    src="https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_800,q_auto,f_auto/{{ site.url }}{{ include.path }}"
        https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_320,q_auto,f_auto/{{ site.url }}{{ include.path }} 320w,
        https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_640,q_auto,f_auto/{{ site.url }}{{ include.path }} 640w,
        https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_960,q_auto,f_auto/{{ site.url }}{{ include.path }} 960w,
        https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_1280,q_auto,f_auto/{{ site.url }}{{ include.path }} 1280w,
        https://res.cloudinary.com/{{ site.cloudinary_cloud }}/image/fetch/c_limit,w_1600,q_auto,f_auto/{{ site.url }}{{ include.path }} 1600w
    sizes="(min-width: 50rem) 50rem, 90vw"
    alt="{{ include.alt }}"
    loading="{{ include.loading | default: "lazy" }}"
{% endif %}

The if statement is so that when working locally I can view images without having to upload them to a place Cloudinary can fetch from. I also have a parameter to allow for lazy loading. The default will always be lazy loading the images but I can optionally specify that they should be eagerly loaded when the image is above the fold.

I hope this is useful to someone out there! It was a fun weekend project that should hopefully further improve the experience for my blog readers.

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