{"action":"opened","issue":{"url":"https://api.github.com/repos/igrigorik/http-client-hints/issues/68","labels_url":"https://api.github.com/repos/igrigorik/http-client-hints/issues/68/labels{/name}","comments_url":"https://api.github.com/repos/igrigorik/http-client-hints/issues/68/comments","events_url":"https://api.github.com/repos/igrigorik/http-client-hints/issues/68/events","html_url":"https://github.com/igrigorik/http-client-hints/issues/68","id":121451447,"number":68,"title":"Unclear on cross-origin interaction & header lifetime","user":{"login":"jakearchibald","id":93594,"avatar_url":"https://avatars.githubusercontent.com/u/93594?v=3","gravatar_id":"","url":"https://api.github.com/users/jakearchibald","html_url":"https://github.com/jakearchibald","followers_url":"https://api.github.com/users/jakearchibald/followers","following_url":"https://api.github.com/users/jakearchibald/following{/other_user}","gists_url":"https://api.github.com/users/jakearchibald/gists{/gist_id}","starred_url":"https://api.github.com/users/jakearchibald/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jakearchibald/subscriptions","organizations_url":"https://api.github.com/users/jakearchibald/orgs","repos_url":"https://api.github.com/users/jakearchibald/repos","events_url":"https://api.github.com/users/jakearchibald/events{/privacy}","received_events_url":"https://api.github.com/users/jakearchibald/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-12-10T10:24:37Z","updated_at":"2015-12-10T10:24:37Z","closed_at":null,"body":"http://igrigorik.github.io/http-client-hints/#advertising-support-for-client-hints\r\n\r\n> When a client receives Accept-CH, it SHOULD append the Client Hint headers that match the advertised field-values. For example, based on Accept-CH example above, the client would append DPR, Width, Viewport-Width, and Downlink headers to all subsequent requests.\r\n\r\nWhat does \"all subsequent requests\" mean in this context? Here's my guess:\r\n\r\n\"subsequent requests with this [client](https://fetch.spec.whatwg.org/#concept-request-client), to the same origin as client, with [destination](https://fetch.spec.whatwg.org/#concept-request-destination) 'subresource' \" - this seems to make the most sense to me. Without the same-origin restriction, the new headers will trigger CORS preflight requests because the new headers aren't [simple](https://fetch.spec.whatwg.org/#simple-header). Servers such as Google Fonts don't support preflights.\r\n\r\nYou probably want a way to opt into client hints for additional origins too."}}