Adding or Including custom post type to default WordPress loop

Adding or Including custom post type to default WordPress loop by altering the ‘pre_get_posts’ function. Here it use add_action() function. This will help to display those posts (custom posts) alongside the default posts in the regular post feed.

Add this in you functions.php file

function add_custom_post_type_to_query( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
    // if ( is_home() ) { // Use this if its not for main query
        $query->set( 'post_type', array('post', '2nd-post-type', '3rd-post-type') );
    }
}
add_action( 'pre_get_posts', 'add_custom_post_type_to_query' );