Stop wordpress from hardcoding img width and height attributes
You can get featured image URL and add it to your content manually, eg: <?php $image = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), ‘thumbnail’ ); if ($image) : ?> <img src=”https://wordpress.stackexchange.com/questions/29881/<?php echo $image[0]; ?>” alt=”” /> <?php endif; ?>