Lazy Loading

WordPress provides lazy loading of images by default as long as width and height attributes are present on an img tag. See the Lazy Loading announcement for more details.

Lazy Loading Inline Frames

Inline frames are lazy-loaded by default using the browser-level loading attribute. Only <iframe> tags with both width and height attributes present will be lazy-loaded to avoid a negative impact on layout shifting. Embedded <iframe> tags provided via oEmbed in content run through the_content, the_excerpt or widget_text_content filters will have the loading="lazy" attribute added by default where the web service has provided a width and height attribute.

You can customize whether and how inline frames are lazy loaded using the wp_lazy_loading_enabled filter. For example, to disable lazy-loading of inline frames from post content entirely, you could use the following code:

add_filter( 'wp_lazy_loading_enabled', function( $default, $tag_name, $context ) {
	if ( $tag_name === 'iframe' && $context === 'the_content'  ) {
		return false;
	}

	return $default;
}, 10, 3 );

You can also use the wp_iframe_tag_add_loading_attr filter to customize a specific <iframe> tag. For example, if you wanted to disable lazy-loading on inline frames from a specific provider, like YouTube, you could use the following code:

add_filter( 'wp_iframe_tag_add_loading_attr', function( $value, $iframe, $context ) {
	if ( $context === 'the_content' && false !== strpos( $iframe, 'youtube.com' ) ) {
		return false;
	}

	return $value;
}, 10, 3 );