Responsive Images: A Complete Developer Guide
How to implement responsive images for optimal performance across devices.
Responsive images serve appropriately sized images based on the viewer device, saving bandwidth on mobile while maintaining quality on large screens.
The Problem
A single image size cannot serve all devices well. A 2000px hero image is wasteful on a 375px mobile screen. Conversely, a 375px image looks blurry on a retina desktop display. Responsive images solve this by providing multiple sizes.
srcset and sizes
The srcset attribute lets you specify multiple image sources with their widths. The sizes attribute tells the browser how wide the image will be displayed at different viewport widths.
Picture Element
The picture element allows you to specify different image sources for different conditions, including different formats. You can serve WebP to supporting browsers and fall back to JPEG for others.
Art Direction
Sometimes you need different crops for different screen sizes. A wide landscape photo might work on desktop but need a tighter crop on mobile. The picture element with media queries handles this.
Lazy Loading
The loading attribute with a value of lazy defers loading of images that are below the viewport. This improves initial page load time significantly for pages with many images. Add loading lazy to all images except those visible in the initial viewport.
Best Practices
Generate multiple sizes of each image (small, medium, large, extra-large). Use our Image Resizer to create consistent sizes. Always include width and height attributes to prevent layout shift. Use WebP format with JPEG fallback for best compression.
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