Content Layout Shift is something I've written about a few times. Surprisingly, this is my first touch on images, the largest culprits of creating CLS!

A page is typically peppered with images throughout. An image can be wholly optimized to be very lightweight, but can still contribute to a negative user experience if the dimensions are not accounted for.

Say you're reading this blog. And a put an image right above this paragraph. If an image FINALLY loads as you're reading this, all of a sudden this paragraph is pushed down and now you have to scroll to find your place. Ugh.

The Solution

The way to mitigate this is pretty simple: Set dimensions on your images.

Easy if you already know what they are: Use css to set explicit widths and heights. You can even use media queries to set them depending on the screen size.

It gets a little trickier if you're doing this dynamically, not knowing what dimensions your image will be. The best bet, then, is to set a container for the image to reside in , and have the image fill the container. Thinking of a div with an img child.

Next Image Component

It's not too involved to code this yourself, but Next.js comes out of the box with a component to handle this along with many other goodies. The Image Component in Next offers Size optimization for local images and lazy loading.

Here I'm using the component for my albums page

import React from 'react';
import Image from 'next/image';
import Link from 'next/link';

const MusicGrid = ({ albums }) => {
  return (
    <>
      <section className="music_display">
        {albums.map((album) => (
          <article key={album.title}>
            {/* <Link href={album.link}> */}
            <Link href={`/${album.slug}`}>
              <a data-test="musicGridLink">
                <Image src={album.coverURL} width="245" height="245" />
                <span>{album.title}</span>
              </a>
            </Link>
          </article>
        ))}
      </section>
    </>
  );
};

export default MusicGrid;

And here is what's generated to the DOM. It's a huge sample, but you can find a few interesting points in there:

The key pieces being the srcset used for different sized images generated for free. These are made with externally sourced images, interestingly enough, but they're generated by the component to handle rendering specifically to the page!

<article>
  <a data-test="musicGridLink" href="/forest"
    ><span
      style="
        box-sizing: border-box;
        display: inline-block;
        overflow: hidden;
        width: initial;
        height: initial;
        background: none;
        opacity: 1;
        border: 0;
        margin: 0;
        padding: 0;
        position: relative;
        max-width: 100%;
      "
      ><span
        style="
          box-sizing: border-box;
          display: block;
          width: initial;
          height: initial;
          background: none;
          opacity: 1;
          border: 0;
          margin: 0;
          padding: 0;
          max-width: 100%;
        "
        ><img
          style="
            display: block;
            max-width: 100%;
            width: initial;
            height: initial;
            background: none;
            opacity: 1;
            border: 0;
            margin: 0;
            padding: 0;
          "
          alt=""
          aria-hidden="true"
          src="data:image/svg+xml,%3csvg%20xmlns=%27http://www.w3.org/2000/svg%27%20version=%271.1%27%20width=%27245%27%20height=%27245%27/%3e" /></span
      ><img
        src="/_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=640&amp;q=75"
        decoding="async"
        data-nimg="intrinsic"
        style="
          position: absolute;
          top: 0;
          left: 0;
          bottom: 0;
          right: 0;
          box-sizing: border-box;
          padding: 0;
          border: none;
          margin: auto;
          display: block;
          width: 0;
          height: 0;
          min-width: 100%;
          max-width: 100%;
          min-height: 100%;
          max-height: 100%;
        "
        srcset="
          /_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=256&amp;q=75 1x,
          /_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=640&amp;q=75 2x
        " /><noscript
        ><img
          srcset="
            /_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=256&amp;q=75 1x,
            /_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=640&amp;q=75 2x
          "
          src="/_next/image?url=https%3A%2F%2Fres.cloudinary.com%2Fcpadilla%2Fimage%2Fupload%2Ft_optimize%2Fchrisdpadilla%2Falbums%2Fforest.jpg&amp;w=640&amp;q=75"
          decoding="async"
          data-nimg="intrinsic"
          style="
            position: absolute;
            top: 0;
            left: 0;
            bottom: 0;
            right: 0;
            box-sizing: border-box;
            padding: 0;
            border: none;
            margin: auto;
            display: block;
            width: 0;
            height: 0;
            min-width: 100%;
            max-width: 100%;
            min-height: 100%;
            max-height: 100%;
          "
          loading="lazy" /></noscript></span
    ><span>Forest</span></a
  >
</article>

Swing Low

09 / 17 / 2023

Music

Listen on Youtube

Sangin'! With Lucy!

Sleepy Seals

09 / 16 / 2023

Art

🤫🦭😴