Responsive image best practices for Drupal

• Determine your image’s aspect ratio. If you find that the images in the design are not in a common aspect ratio (like 1:1, 2:1, 4:3, or 16:9) or if they vary by a little bit, consider running the dimensions through a tool that will find the closest reasonable aspect ratio.
• Determine the smallest and largest image sizes. For example, for a 16:9 aspect ratio, the smallest size might be 320 pixels x 180 pixels, while the largest could be 3,200 pixels x 1,800 pixels (doubled for high-density screens).
• To generate all variations, you can use an AI tool to print images with 160-pixel increments between each size. 160 increments tend to hit a lot of common breakpoints. Here’s an example using GitHub CoPilot:

There are likely more ways to streamline this process with Copilot. I’ve also used ChatGPT to rewrite them using a prefix, making it easy to add them in Drupal like this:

If adding all of these steps seems like a lot of work, consider using the Easy Responsive Images module! This module can create image styles for you, allowing you to set your aspect ratios and the increment between each style.

Once you have all your styles in place, create your responsive image styles by following these steps:

• Choose a name for your responsive image style based on its usage
• Select the “responsive image” breakpoint group
• Usually, I choose to select multiple image styles and use the sizes attribute. Use the sizes attribute to craft your “sizes.” For example:

(min-width:960px) 50vw, (min-width:1200px) 30vw, 100vw

In this example, choosing an image that is smaller than 960 pixels will best fit the full width of the viewport. At 960 pixels, the image will be selected to best fill half of the viewport width, and at 1,200 pixels, 30%. This approach is nimble and allows the browser to choose the most appropriate image for each case.

After setting the size rules, choose all of the image styles that you want the browser to be able to use. You don’t have to use them all. In some cases, you might have two responsive image styles that are pulling from the same aspect ratio image styles, but one uses all of them and the other uses a subset of them.

After adding your responsive image style, you need to map your Media View Mode:

1. Go to https://[your-site.local]/admin/structure/display-modes/view/add/media
2. Add the media view mode as a new Display for Images: https://[your-site.local]/admin/structure/media/manage/image/display
3. Choose “Responsive image” as the Format and select your new responsive image style

Once you have set this up, you are ready to use the View Mode to display the image field for your entity.

In this example, all the images have the same breakpoint. There may be times when you need to have different aspect ratios at different breakpoints. In those cases, you may want to use your custom theme’s Breakpoint Group. This will allow you to manually select each image style on for each breakpoint (instead of letting Drupal choose it for you).