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Properly size images

May 2, 2019

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Updated Jun 20, 2020 Appears in :Performance audits The Opportunities part of your Lighthouse report lists all images in your page that are n’t appropriately sized, along with the potential savings in kibibytes ( KiB ). Resize these images to save data and improve page load time :

How Lighthouse calculates oversized images #

For each prototype on the page, Lighthouse compares the size of the render effigy against the size of the actual picture. The hand over size besides accounts for device pixel ratio. If the try size is at least 4KiB smaller than the actual size, then the image fails the audit .

Strategies for properly sizing images #

ideally, your page should never serve images that are larger than the version that ‘s rendered on the exploiter ‘s screen. Anything larger than that merely results in otiose bytes and slows down foliate load meter. The main strategy for serving appropriately sized images is called “ reactive images ”. With responsive images, you generate multiple versions of each image, and then specify which version to use in your HTML or CSS using media queries, viewport dimensions, and so on. See Serve reactive images to learn more. picture CDNs are another chief scheme for serving appropriately sized images. You can think of trope CDNs like web avail APIs for transforming images. Another strategy is to use vector-based persona formats, like SVG. With a finite sum of code, an SVG effigy can scale to any size. See Replace complex icons with SVG to learn more.

Tools like gulp-responsive or responsive-images-generator can help automate the process of converting an trope into multiple formats. There are besides trope CDNs which let you generate multiple versions, either when you upload an effigy, or request it from your page. Use the amp-img part ‘s digest for srcset to specify which image assets to use based on the screen size. See besides Responsive images with srcset, sizes & heights. Consider using the BreakpointObserver utility in the Component Dev Kit ( CDK ) to manage trope breakpoints. Use the built-in Responsive Image Styles feature ( available in Drupal 8 and above ) when rendering visualize fields through view modes, views, or images uploaded through the WYSIWYG editor. Use the gatsby-image plugin to generate multiple smaller images for smartphones and tablets. It can besides create SVG image placeholders for effective faineant load. Consider using a responsive images plugin.

upload images directly through the media library to ensure that the want image sizes are available, and then insert them from the media library or use the double doodad to ensure the optimum image sizes are used ( including those for the responsive breakpoints ). Avoid using Full Size images unless the dimensions are adequate for their use. See tuck images into posts and pages. final update : Jun 20, 2020Improve article