Your WordPress theme might have multiple loops in the page. For example, there may be a ‘Featured’ section at the top of your homepage, and a ‘Recent Posts’ section below that.

These are separate loops, but could contain the same post. For example, your most recent post might also be in the Featured category.

You only want the post to appear once. How do you manage it?

Avoid showing duplicate WordPress posts
The answer is surprisingly simple. Put the following in your functions.php.

add_filter(‘post_link’, ‘track_displayed_posts’);

$displayed_posts = [];

function track_displayed_posts($url) {
global $displayed_posts;
$displayed_posts[] = get_the_ID();
return $url; // don’t mess with the url

function remove_already_displayed_posts($query) {
global $displayed_posts;
$query->set(‘post__not_in’, $displayed_posts);

We only want to hide posts which have been displayed already – so we hook into the post_link() function call and make a note of the post we’re displaying.

We then want to hook into any new WordPress query to tell the query to not include any of the posts we’ve already seen. We do this by hooking into the pre_get_posts function and passing it our list of already-displayed posts.