تفصیل

Lazy Loading Feature Plugin is an official plugin maintained by the WordPress team. It is intended for testing of automatically adding the loading HTML attribute to images and other elements that support it.

More information about the loading attribute:
Description: https://developer.mozilla.org/en-US/docs/Web/HTML/Element/img#attr-loading.
HTML Specification: https://html.spec.whatwg.org/multipage/embedded-content.html#attr-img-loading.

Currently the loading attribute is supported in the following browsers: https://caniuse.com/#feat=loading-lazy-attr.

To test, install and enable the plugin. It will automatically add loading="lazy" attributes to all images in all new and existing posts, pages, and text widgets on the front-end.

Then use one of the browsers that support it (Chrome, Opera, Firefox, Edge, Android, etc.) and visit the site. Best would be to test over a slower connection, with a phone, etc. and test web pages that have a lot of images, like gallery posts.

Things to look for

• Obvious bugs, for example images are missing.
• Try to scroll down as soon as the page loads. All images should be at their places, and the page shouldn’t “jump” when images are loaded.

Note to developers

This plugin is intended for testing. If the tests are successful, this functionality will be added to WordPress, but the exact code may change, perhaps significantly.

When testing, please also test the filters added by this plugin, and provide feedback at https://github.com/WordPress/wp-lazy-loading or at https://core.trac.wordpress.org/ticket/44427.