To implement progressive enhancement for AVIF, use the picture element. This is different from WebP which doesn't always produce smaller images than JPEG and may actually be a net-loss due to lack of support for progressive loading.įor more info on AVIF encoding and quality settings, check out my dedicated blog post. Safari support isn't available yet, but given that Apple is a member of the group that is behind the format, we can expect future support.ĪVIF is notable because it very consistently outperforms JPEG in a very significant way. It is currently supported in Chromium browsers, and available behind a flag in Firefox. */ĪVIF is the most recent image format that has gained adoption in web browsers. * This probably only makes sense for images within the main scrollable area of your page. Other browser engines do not yet () implement content-visibility: auto and would presumably follow Chromium's lead on this special case.
LOADING PICTURE HOW TO
Update contain-intrinsic-size no longer needed #Īn earlier version of this post explained how to use contain-intrinsic-size to avoid CLS impact of content-visibility: auto but as of Chromium 88 this is no longer needed for images that provide width and height as explained above. This has all kinds of benefits, but the most important one might be that the browser will not bother decoding our blurry placeholder image or the image itself unless it has to, saving CPU. The new CSS attribute content-visibility: auto instructs the browser to not bother layouting the image until it gets near the screen. The second technique is more cutting edge. This avoids Cumulative Layout Shift (CLS). New in 2020 is that web browsers will reserve the correct vertical space for the image before it loads if the width and height attributes are provided for the img element. This is a well understood technique to make an image use the available horizontal space up until its maximum size while retaining the aspect ratio. Optimization techniques # Responsive layout # View the source of this sample image to see all the techniques in action: Reducing First Input Delay(FID) through reduced (main-thread) CPU usage.Keeping Cumulative Layout Shift (CLS) to zero.Minimizing the Largest Contentful Paint (LCP) through reducing bytes, caching, and lazy loading.Together the techniques optimize all elements of Google's Core Web Vitals by I'll keep a list updated at the end of this posts with technologies that provide all of the optimizations outlined here. Ideally, your favorite mechanism for publishing web documents (like a CMS, static site generator, or web application framework) implements all of these out-of-the-box. Some of these techniques are more established, while others are somewhat novel. I'll present them in the form of an annotated HTML example to make it easy for folks to reproduce the results. In this post I'll outline 8 image loading optimization techniques to minimize both the bandwidth used for loading images on the web and the CPU usage for image display.
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