Why it matters
Heavy images dominate page weight on content pages and slow LCP on constrained networks.
How to fix it
Serve AVIF/WebP, size images to their rendered width with srcset + sizes, and lazy-load images below the fold.
More performance rules
void perf reports 25 rules in this category. Core Web Vitals and bytes: LCP, CLS, TBT, TTFB, JavaScript, CSS, fonts, images, caching and compression, measured as the median of several runs on a throttled mobile and a desktop profile.
js-budgetFirst-load JavaScript exceeds the budgetcss-budgetCSS transfer exceeds the budgetfont-budgetWeb font transfer exceeds the budgettoo-many-fontsToo many font files are downloadedtoo-many-requestsPage makes many requestslcp-image-lazyLCP image is lazy-loadedlcp-image-no-priorityLCP image has no fetchpriority="high"lcp-background-imageLCP element is a CSS background image