How to Disable the New WordPress Block Style CSS in 3 Lines

If you don’t use the new WordPress blocks, you should avoid loading the block-style CSS on your page to optimize the page load speed. Here are the three lines you need:

add_action('wp_print_styles', function () {
  wp_dequeue_style('wp-block-library');
  wp_dequeue_style('wp-block-library-theme');
}, 100);

Adding the action with priority 100, it will be executed after the style has been enqueued by WordPress.

You can add this code in your functions.php theme file.