WebP
A modern image format with lossy, lossless and transparency support, smaller than JPEG or PNG.
WebP is an image format that produces files roughly 25 to 35 percent smaller than an equivalent JPEG or PNG, with support for transparency and animation. Every current browser supports it, so converting images to WebP is one of the largest reductions in page weight available for the least effort.
Definition
WebP is an image format developed by Google that supports both lossy and lossless compression plus transparency, replacing the JPEG/PNG split with one format. Files are typically substantially smaller than an equivalent-quality JPEG or PNG.
Browser support is universal among current browsers. AVIF compresses better still but encodes more slowly and has slightly narrower support, so a common arrangement is AVIF first, WebP second, JPEG or PNG as the final fallback.
Why It Matters
Converting existing images to WebP is one of the few site-wide performance improvements that requires no design decisions and no content changes. The page looks the same and weighs less.
Because images usually dominate page weight, the effect lands directly on LCP — the metric most often responsible for a failing Core Web Vitals assessment.
Example
Serve it with a fallback so nothing breaks:
<picture>
<source srcset="/hero.avif" type="image/avif">
<source srcset="/hero.webp" type="image/webp">
<img src="/hero.jpg" width="1200" height="630" alt="…">
</picture>One exception worth remembering: social preview images should stay PNG or JPEG, because several platforms will not render WebP or SVG in a share card.
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