+https://wp-snippet.com/snippets/show-popular-posts-without-plugin/

Heres a little trick on how to show a list of the most popular WordPress post by post read count – without using a plugin.

function count_post_visits() {
 if( is_single() ) {
 global $post;
 $views = get_post_meta( $post->ID, 'my_post_viewed', true );
 if( $views == '' ) {
 update_post_meta( $post->ID, 'my_post_viewed', '1' ); 
 } else {
 $views_no = intval( $views );
 update_post_meta( $post->ID, 'my_post_viewed', ++$views_no );
 }
 }
}
add_action( 'wp_head', 'count_post_visits' );

Then add this anywhere in your template where you wish to display the posts.

<?php 
$popular_posts_args = array(
 'posts_per_page' => 3,
 'meta_key' => 'my_post_viewed',
 'orderby' => 'meta_value_num',
 'order'=> 'DESC'
);
 
$popular_posts_loop = new WP_Query( $popular_posts_args );
 
while( $popular_posts_loop->have_posts() ):
 $popular_posts_loop->the_post();
 // Loop continues
endwhile;
wp_reset_query();

?>