If portals really were iframes, there would be no reason to create them. Google is completely open about their intentions. Citation from https://github.com/WIC

If portals really were iframes, there would be no reason to create them. Google is completely open about their intentions. Citation from https://github.com/WICG/portals/blob/master/key-scenarios.md https://github.com/WICG/portals/blob/master/key-scenarios.md: > After being activated, a portal opened by the news aggregator will now receive the input events. This means that it will have to co-operate with the news aggregator in order to maintain the desired user experience. Why exactly does it _have_ to cooperate? And _how_ can it cooperate? Will it be enough to include a script from parent domain? Will analytics be part of "desired user experience"? Will parent domain ban a site from it's index for trying to "break out"? It is essentially impossible to build relationships of mutual trust to the point when one website can freely embed another... unless one party has overwhelming power advantage. Who is the target auditory of <portal>? What "news aggregator" has enough leverage to make pages switch back to it as told to? If such "aggregator" existed, I would not trust it to make web browsers or dictate, how they should work.