What is resource prioritization in browsers?

Browsers assign priorities to resource fetches based on type and location. High priority: HTML, CSS (render-blocking), scripts at head, fonts, preloaded resources. Medium: images in viewport, regular scripts, AJAX. Low: images offscreen, scripts with defer. Fetch Priority API (priority hints): explicitly set priority: <img fetchpriority="high" src="lcp-hero.jpg"> for the LCP image. <script fetchpriority="low" src="analytics.js">. <link rel="preload" as="script" fetchpriority="low"> for less critical preloads. LCP image priority: the LCP image should be fetchpriority="high" — the browser's default priority for above-fold images may not be high enough. Importance of prioritization: browsers have limited concurrent connections even with HTTP/2 multiplexing. Correct prioritization ensures the resources that affect user perception (LCP element, interactive scripts) download first. Browser priority is often correct by default — only override when you have specific knowledge that the browser's heuristics are wrong for your page.