WordPress.org

This plugin optimizes the loading of images (and videos) with prioritization to improve <a href="https://web.dev/articles/lcp" rel="nofollow ugc">Largest Contentful Paint</a> (LCP), lazy loading, and more accurate image size selection.
The current optimizations include:
<ol>
<li>Add breakpoint-specific <code>fetchpriority=high</code> preload links (both as <code>LINK[rel=preload]</code> elements and <code>Link</code> response headers) for image URLs of LCP elements:
<ol>
<li>An <code>IMG</code> element, including the <code>srcset</code>/<code>sizes</code> attributes supplied as <code>imagesrcset</code>/<code>imagesizes</code> on the <code>LINK</code>.</li>
<li>The first <code>SOURCE</code> element with a <code>type</code> attribute in a <code>PICTURE</code> element. (Art-directed <code>PICTURE</code> elements using media queries are not supported.)</li>
<li>An element with a CSS <code>background-image</code> inline <code>style</code> attribute.</li>
<li>An element with a CSS <code>background-image</code> applied with a stylesheet (when the image is from an allowed origin).</li>
<li>A <code>VIDEO</code> element’s <code>poster</code> image.</li>
</ol>
</li>
<li>Ensure <code>fetchpriority=high</code> is only added to an <code>IMG</code> when it is the LCP element across all responsive breakpoints.</li>
<li>Add <code>fetchpriority=low</code> to <code>IMG</code> tags which appear in the initial viewport but are not visible, such as when they are subsequent carousel slides.</li>
<li>Lazy loading:
<ol>
<li>Apply lazy loading to <code>IMG</code> tags based on whether they appear in any breakpoint’s initial viewport.</li>
<li>Implement lazy loading of CSS background images added via inline <code>style</code> attributes.</li>
<li>Lazy-load <code>VIDEO</code> tags by setting the appropriate attributes based on whether they appear in the initial viewport. If a <code>VIDEO</code> is the LCP element, it gets <code>preload=auto</code>; if it is in an initial viewport, the <code>preload=metadata</code> default is left; if it is not in an initial viewport, it gets <code>preload=none</code>. Lazy-loaded videos also get initial <code>preload</code>, <code>autoplay</code>, and <code>poster</code> attributes restored when the <code>VIDEO</code> is going to enter the viewport.</li>
</ol>
</li>
<li>Responsive image sizes:
<ol>
<li>Compute the <code>sizes</code> attribute using the widths of an image collected from URL Metrics for each breakpoint (when not lazy-loaded since then handled by <code>sizes=auto</code>).</li>
<li>Ensure <a href="https://make.wordpress.org/core/2024/10/18/auto-sizes-for-lazy-loaded-images-in-wordpress-6-7/" rel="nofollow ugc"><code>sizes=auto</code></a> is set on <code>IMG</code> tags after setting correct lazy-loading (above).</li>
</ol>
</li>
<li>Reduce the size of the <code>poster</code> image of a <code>VIDEO</code> from full size to the size appropriate for the maximum width of the video (on desktop).</li>
</ol>
This plugin requires the <a href="https://wordpress.org/plugins/optimization-detective/" rel="ugc">Optimization Detective</a> plugin as a dependency. Please refer to that plugin for additional background on how this plugin works as well as additional developer options.
👉 Note: This plugin optimizes pages for actual visitors, and it depends on visitors to optimize pages. As such, you won’t see optimizations applied immediately after activating the plugin. Please wait for URL Metrics to be gathered for both mobile and desktop visits. And since administrator users are not normal visitors typically, optimizations are not applied for admins by default.
Your site must have the REST API accessible to unauthenticated frontend visitors since this is how metrics are collected about how a page should be optimized. There are currently no settings and no user interface for this plugin since it is designed to work without any configuration.

Image Prioritizer

Prioritizes the loading of images and videos based on how they appear to actual visitors: adds fetchpriority, preloads, lazy-loads, and sets sizes.

Oxyplug Team

<ul>
<li>Supported only on Chromium-based browsers since version 121+</li>
<li>In the post/product category pages, first X items will be prefetched before the user clicks. The default value for X is 4 items and can be adjusted via the plugin settings.</li>
<li>If a user hovers over a link, the destination page will be prefetched before click. Please note that this option is disabled by default and can be enabled via the plugin settings.</li>
<li>It is also possible to prefetch some custom links on posts/products by entering preferred URLs.</li>
<li>Similar actions can be applied with prerender.</li>
</ul>

Oxyplug Prefetch & Prerender

Faster loading next pages by prerendering/prefetching all links a user hovers or addresses you prefer. It improves UX and Core Web Vitals score.

Image Prioritizer vs Oxyplug Prefetch & Prerender