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Category: WEB DESIGN

Implementing WebP images in Jekyll

How I added WebP images to my Jekyll-based static site, obtaining new levels of optimization and performance.

What is WebP

WebP is a modern image format that provides superior lossless and lossy compression for images on the web. […] WebP lossless images are 26% smaller in size compared to PNGs. WebP lossy images are 25-34% smaller than comparable JPEG images at equivalent quality index. An image format for the Web, by Google

Implementation

I have three ways of adding images:

  • through a figure module
  • through a responsive images module
  • using a simple img tag

I just had to tweak the first two files under my _includes folder and reach out for the few spare img tags (mostly connected to my Indieweb integration).

Example: Figure module

Before

<figure class="{{ include.class | default: 'my-5 text-center' }}">
  <img class="mx-auto" src="{{ include.image }}" alt="{{ include.alt | default: include.caption }}" {{ include.width ? include.width | prepend: 'width="' | append: '"' }} {{ include.height ? include.height | prepend: 'height="' | append: '"' }}>
  {% if include.caption %}<figcaption class="p-name mt-3 caption">{{ include.caption }}</figcaption>{% endif -%}
</figure>

After

I created a picture element containing all the srcset needed for a full support. Although WebP is supported on all major browsers, I’m serving fallbacks to older versions.

<figure class="{{ include.class | default: 'my-5 text-center' }}">
  <picture>
    <source srcset="{{ include.image | replace:'.png','.webp' | replace:'.jpg','.webp' | replace:'.jpeg','.webp' }}" type="image/webp">
    <source srcset="{{ include.image }}" {% if include.image contains '.jpg' or include.image contains '.jpeg' %}type="image/jpeg"{% elsif include.image contains '.png' %}type="image/png"{% endif %}>
    <img class="mx-auto" src="{{ include.image }}" alt="{{ include.alt | default: include.caption }}" {{ include.width ? include.width | prepend: 'width="' | append: '"' }} {{ include.height ? include.height | prepend: 'height="' | append: '"' }}>
  </picture>
  {% if include.caption %}<figcaption class="p-name mt-3 caption">{{ include.caption }}</figcaption>{% endif -%}
</figure>

Results

I got a double 100% on GTMetrix, and improved my 512k club rank. I cut the loading time by a considerable amount in pages with multiple images. I’m now serving responsive images where needed, in WebP format where supported.