How to order by random

To sort results randomly in a listing template query, you can set the orderby query argument to rand, and order to ASC.

If you are using a custom WP_Query for your listing template, you can set the argument directly in its query arguments. When using a WP archive template, you can add it with a pre_get_posts filter.

And if you are using a Listing Builder template in dev mode, you can add it to the query arguments like this:

How to use custom PHP code?
PHP code can be added to your (child) theme's functions.php file. Alternatively, you can use the Custom Hooks add-on, or a code snippets plugin. More info
<?php
return [
  'post_type' => [
    "post"
  ],
  'post_status' => [
    'publish'
  ],
  'posts_per_page' => 10,
  'orderby' => [
    'rand' => 'ASC', // Sort by random
    'title' => 'ASC' // Use post title as a fallback sort
  ]
];

See the official WP_Query documentation for more info about query arguments and other values to sort posts by.

Fix duplicate posts and pagination issues

Since FacetWP is AJAX-based, the problem with random ordering is that the results will be re-randomized on each facet interaction that fetches posts (including paging and sorting), which will lead to duplicate posts and other issues.

Fortunately, this can be fixed by adding the following code to your (child) theme’s functions.php:

How to use custom PHP code?
PHP code can be added to your (child) theme's functions.php file. Alternatively, you can use the Custom Hooks add-on, or a code snippets plugin. More info
<?php
function preserve_random_order( $orderby ) {
  $seed = floor( time() / 10800 ); // randomize every 3 hours
  $orderby = str_replace( 'RAND()', "RAND({$seed})", $orderby );
  return $orderby;
}
add_filter( 'posts_orderby', 'preserve_random_order' );

See also