Currently we are in the process of securing our web sites. we are experiencing issue on Xhtml Validator in RadEditor where it is not properly loading due to mixed content issue. There is no way to redirect to HTTPS instead of HTTP site. We can reproduce this on Rad Editor Demo site by making site as HTTPS and click on XHTML Validator icon. https://demos.telerik.com/aspnet-ajax/editor/examples/overview/defaultcs.aspx Could you please add that feature?