> how do you make sure browser clients are talking to the right api backend version? We version the URL itself. > How do you force them to upgrade or rollback

> how do you make sure browser clients are talking to the right api backend version? We version the URL itself. > How do you force them to upgrade or rollback? We don't use it often but we can embed an "obsolete" tag into the HTTP/AJAX response header which a global AJAX hook (jQuery) will read and bring up a prompt/force a page reload. We use it infrequently but it was added for just such an occasion. It is a bad user experience but it is a useful tool.