How to display related products only the primary category (product carousel element)

Dear @kmc,

We hope this message finds you well.

As an alternative, you may consider using the following filter: woocommerce_related_products_args

Please find the example code below for your reference:

$args = apply_filters( 'woocommerce_related_products_args', array(
    'post_type'           => 'product',
    'ignore_sticky_posts' => 1,
    'no_found_rows'       => 1,
    'posts_per_page'      => $posts_per_page,
    'orderby'             => $orderby,
    'post__in'            => $related,
    'post__not_in'        => array( $product->get_id() )
) );

Should you have any further questions or require additional assistance, please do not hesitate to reach out.

Best regards,
The 8Theme Team

Dear @kmc,

We hope this message finds you well.

Please try using the following code snippet to filter related products by the primary category:

add_filter( 'woocommerce_products_widget_query_args', 'filter_related_products_by_primary_category', 999, 1 );

function filter_related_products_by_primary_category( $args ) {
    global $product;
    if ( ! $product ) {
        return $args;
    }

    // 1. Get Yoast Primary Category
    $primary_cat_id = get_post_meta( $product->get_id(), '_yoast_wpseo_primary_product_cat', true );

    // 2. If no primary category is set, fall back to the default
    if ( ! $primary_cat_id ) {
        $terms = wp_get_post_terms( $product->get_id(), 'product_cat' );
        if ( ! empty( $terms ) && ! is_wp_error( $terms ) ) {
            $primary_cat_id = $terms[0]->term_id;
        }
    }

    // 3. Add tax_query to filter by category
    if ( $primary_cat_id ) {
        $args['tax_query'][] = array(
            'taxonomy' => 'product_cat',
            'field'    => 'term_id',
            'terms'    => array( $primary_cat_id ),
        );
    }

    return $args;
}

Please note that any further customization beyond this may fall outside the scope of our standard support services.

Thank you for your understanding.

Best regards,
The 8Theme Team