With third-party cookies turned off, youtube.com definitely shouldn't be able to show your logged-in state from a google.com server. They generally play some fa

With third-party cookies turned off, youtube.com definitely shouldn't be able to show your logged-in state from a google.com server. They generally play some fancy footwork with redirects to deliberately break third-party cookie origin parties so that they can achieve "single sign-in". I, personally, would prefer it if this were not possible, but it seems unlikely that Google would find this a desirable outcome. Personally, I isolate my logged-in Google services in their own separate browser. I was hoping to find (or write) a browser plugin which opens URLs in different browsers based on regex of some sort (i.e. *.google.com, gmail.com, youtube.com links open in Chrome, everything else in Firefox), but I believe this is difficult to achieve because of the way browser sandboxing works (at least in Chrome).