How to use native loading="lazy" for images and iframes without breaking LCP. Covers Chrome 2026 heuristics, fetchpriority combos, iframe deferral, CLS prevention, and SEO.
Tag any image, price, or button with elementtiming and read its real paint timestamp from PerformanceObserver. Practical RUM setup, cross-origin gotchas, and the new Container Timing trial.
The fetchpriority attribute is one of the most precise tools for shaping browser resource loading. Used right, it can shave 200-800ms off your LCP without touching CSS or JavaScript. Here's every legitimate use case, the mistakes that quietly hurt performance, and how to measure real-world impact.