With a WordPress Child theme, you can easily change core behavior and override certain files…
- Go to settings – media and set all sizes of those you dont need to 0 (zero) to diasable them.
- If you use a theme like “Total” disable the additional image sizes option since you only want the native original ones.
- Install the “Force Regenerate Thumbnails” plugin since this is the only one which also deletes the files for the now unnecessary image sizes.
- If you want more, now head over to your functions.php fiel and add this line of code to also remove the new wordpress core hidden image size 768px (read more)
add_filter( 'intermediate_image_sizes', '__return_empty_array', 999 );
- Now finally go to “Tools” – “Force Regenerate Thumbnails” and regenerate everything.
- Afterwards I would recommend to now also further comporess the remaining images with a plugin like “EWWW Image Optimizer”