Preload
Preload is a web performance optimization technique that allows developers to hint to the browser about critical resources (like fonts, scripts, or stylesheets) that will be needed soon, enabling the browser to fetch them early without blocking rendering. It is implemented using the <link rel="preload"> HTML element or the Link HTTP header, specifying resources with their type and priority. This helps reduce latency and improve page load times by loading essential assets in advance.
Developers should use Preload when they have critical resources that are discovered late in the rendering process, such as fonts loaded via @font-face, scripts for interactivity, or stylesheets for above-the-fold content, to prevent render-blocking delays. It is particularly useful for single-page applications (SPAs) or media-rich sites where performance is crucial, as it allows prioritization of key assets over less important ones, enhancing user experience and Core Web Vitals scores like Largest Contentful Paint (LCP).