@SteveJessop, be sure to provide a hyperlink to "Javascript hacks that enable a completely unrelated site to check no matter whether a given URL is within your background or not" You can not normally depend on privacy of the entire URL both. As an example, as is usually the case https://dominickecvov.digitollblog.com/37295229/the-fact-about-uk-copyright-application-service-that-no-one-is-suggesting