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What Are Priority Hints?

Priority Hints is a specification in the realm of web performance, currently a draft in the W3C (World Wide Web Consortium). This feature provides developers with a method to signal the relative importance of resources to the browser, thereby influencing the order in which resources are downloaded and processed and affecting the performance of your website as well.

Typically, a web browser determines the priority of resource loading based on the type of resource, its location in the document, and other factors. However, these heuristics may not always align with the actual priorities from the perspective of the webpage's layout or the user's experience. Priority Hints allows developers to communicate these priorities more directly, potentially leading to more efficient network use and faster page rendering.

Priority Hints are implemented using the importance attribute, which can be added to HTML elements that fetch resources, such as <img>, <link>, and <script>. The importance attribute can take one of three values:

  1. High. The resource is of high importance to the page's layout or functionality.
  2. Low. The resource is of low importance, and its loading can be deferred without significantly impacting the user experience.
  3. Auto. The browser should determine the importance of the resource using its default heuristics.

Keep in mind that Priority Hints is an advisory signal to the browser. The browser maintains the final decision on resource prioritization and can ignore or override these hints based on internal logic or constraints, such as network conditions.

Explore Priority Hits more at this GitHub link.

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