Output WebP mini plugin

output-webp.php

<?php
/**
 * Outout WebP sub size images.
 *
 * @wordpress-plugin
 * Plugin Name: WebP-only.
 * Description:  Output WebP sub size images.
 * Plugin URI:
 * Version:     1.0.0
 * Author:      Adam Silverstein, Google
 * License:     Apache License 2.0
 * License URI: https://www.apache.org/licenses/LICENSE-2.0
 */
 
function filter_image_editor_output_format( $mappings ){
	$mappings[ 'image/jpeg' ] = 'image/webp';
	return $mappings;
}
add_filter( 'image_editor_output_format', 'filter_image_editor_output_format' );