Force a particular format for images

optimole-optml-forced-format.php

<?php
/* 
Plugin Name: Optimole Tweak - Force a format for all images
Version: 0.0.1
Requires PHP: 7.0
Author URI: https://optimole.com
*/

function optml_forced_format() {
	
add_filter( 'optml_image_args', 
	   function( $args, $original_url ) {
         $args['format'] = 'jpg'; // replace jpg with the format you want e.g png,jpg,webp,avif
       
	return $args;		
		}, 
	   PHP_INT_MAX, 2 );
}
optml_forced_format();