Responsive Images Without Slowing Down Mobile Pages

Large images are a frequent cause of slow mobile pages. A responsive image strategy serves an appropriate asset size instead of forcing every visitor to download the largest version.

Use srcset and sizes when you have multiple widths of the same image. The browser can select a suitable candidate based on the viewport and device pixel ratio. Set width and height attributes to reserve space and reduce layout shifts. Use descriptive alt text for meaningful images, while decorative images should have empty alt text.

Modern formats such as WebP or AVIF can reduce transfer size, but keep a delivery path compatible with your audience and image pipeline. Lazy-load below-the-fold images; do not lazy-load the main hero image if it is likely to be the largest contentful paint element.

Measure actual results with browser performance tools and field data. Image compression is useful, but a page can remain slow because of render-blocking scripts, oversized fonts, or an overloaded server. Treat image optimization as one part of the performance budget.