[webkit-dev] Request for Position: Origin-Agent-Cluster default / deprecating document.domain

Daniel Vogelheim vogelheim at chromium.org
Thu Dec 9 10:41:06 PST 2021

Hello webkit-dev,

I'd like to get your position on assigning documents to origin-keyed agent
clusters by default. This would effectively deprecate document.domain
setting, and make it available only as an opt-in feature.

Explainer: https://github.com/mikewest/deprecating-document-domain

We'd like to change the treatment of Origin-Agent-Cluster
<https://html.spec.whatwg.org/multipage/origin.html#origin-isolation> so
that the default - an absent or malformed header - would be treated as
enabling origin-keyed agent clusters. This would turn the
Origin-Agent-Cluster:-header from an opt-in into an opt-out feature. As a
consequence, browsers could origin-isolate more pages.
The developer-visible consequence is that modifying document.domain in
order to relax same-origin restrictions, which is already deprecated
<https://html.spec.whatwg.org/#relaxing-the-same-origin-restriction>, will
turn into an opt-in feature that must be explicitly requested.

Further info:
TAG discussion on the subject:
Explainer: https://github.com/mikewest/deprecating-document-domain
HTML Spec on Origin-Agent-Cluster:
HTML Spec on document.domain:
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