Custom WordPress RSS – Just One Category

If you want your main RSS feed to include only posts in a certain category, add the code below to your theme’s functions.php file, substituting CategoryNameHere for the category you want.

I found this in a 2009 post on Will Anderson’s blog.

add_filter('pre_get_posts', 'filterRSSQuery');
function filterRSSQuery($query) {
  if ( $query->is_feed ) {
      $query->set('category_name', 'CategoryNameHere');
  }
  return $query;
}