Origin-keyed agent clusters allows developers to opt in to giving up certain cross-origin same-site access capabilities — namely synchronous scripting via document.domain, and postMessage()ing WebAssembly.Module instances. This gives the browser more flexibility in implementation technologies. In particular, in Chrome, we will use this as a hint to put the origin in its own process, subject to resource or platform limitations.


Certain legacy features prevent us from aligning the process boundary with the origin boundary, meaning that sometimes origins share a process with other origins. Origin-keyed agent clusters allows developers to voluntarily give up these legacy features, in exchange for potentially getting their own process. Reasons why a site may want a separate process include: performance isolation, allocations of large amounts of memory, and improved memory measurement.



Specification link

Specification being incubated in a Community Group

Status in Chromium


Enabled by default (tracking bug)

Consensus & Standardization

After a feature ships in Chrome, the values listed here are not guaranteed to be up to date.


Intent to Prototype url

Intent to Prototype thread


This feature was originally known as "origin isolation", but was renamed per the discussion in https://github.com/whatwg/html/issues/6192.

Search tags

origin-agent-cluster, origin, header,

Last updated on 2021-12-13