Image Compression (WebP & AVIF)
WebP and AVIF are modern image formats that reach markedly smaller file sizes than JPEG or PNG at comparable visual quality, and so reduce a website's data volume and load time. They only improve LCP to the extent that the image download is genuinely the bottleneck.
In practice
Both formats are supported by most modern browsers. The `` element additionally allows a JPEG or PNG fallback for older browsers, so that the speed advantage is used without putting compatibility at risk. For LCP, keep this in mind: according to Google, most websites with poor LCP spend less than ten per cent of that time downloading the LCP image – server response time and the moment the browser requests the image at all weigh far more heavily. A modern image format is therefore sensible basic hygiene, but it replaces neither a fast server response nor an early, high-priority request for the main image.