Responsive Image Delivery: The <picture> Tag, srcset, and Modern Format Fallbacks
Master responsive image delivery in HTML using the <picture> element and srcset attribute to serve WebP with fallback JPEGs to legacy browsers.
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The HTML <picture> element and srcset attribute enable web browsers to negotiate image formats and resolutions automatically. By combining <source type="image/webp"> with a fallback <img> pointing to JPEG or PNG, web developers can deliver next-gen lightweight formats to modern browsers while maintaining 100% backward compatibility for legacy clients.
1. The Syntax: <picture> with Format Negotiation
Here is the standard production pattern for delivering modern WebP imagery with universal JPEG fallbacks:
<picture>
<!-- Modern browser: WebP -->
<source srcset="/images/hero.webp" type="image/webp" />
<!-- Legacy fallback: JPEG -->
<img
src="/images/hero.jpg"
alt="Squeeze In-Browser Converter"
width="1200"
height="630"
loading="lazy"
/>
</picture>2. Viewport Width Switching with srcset
For mobile responsive design, combine format negotiation with width descriptors (w) and the sizes attribute:
<img srcset="/hero-400.webp 400w, /hero-800.webp 800w, /hero-1200.webp 1200w" sizes="(max-width: 600px) 100vw, (max-width: 1200px) 50vw, 1200px" src="/hero-800.webp" alt="Responsive hero asset" />
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