ERR (ER by reach)

ERR is the engagement rate by reach. It is calculated as the sum of likes, comments, and shares on a post, divided by its total reach, multiplied by 100%. For VKontakte, total reach is follower reach plus viral reach; for Facebook and Instagram, overall reach is used.

Unlike ER post, ERR does not depend on audience size and shows post quality — how actively people who actually saw it react. Available only for pages you administer.