Currently, the server has no way of knowing whether a particular document request was initiated from an iframe without storage access. Many applications wish to serve a different page when the requested frame does not have storage access, to prompt the user for access (for example, we do this in Google Docs on Safari and Firefox). Currently, we’re forced to do this check on the client. It would be preferable if there could be a request header indicating whether the given request is from a context that does not have storage access.