Window: originAgentCluster property

The originAgentCluster read-only property of the Window interface returns true if this window belongs to an origin-keyed agent cluster: this means that the operating system has provided dedicated resources (for example an operating system process) to this window's origin that are not shared with windows from other origins.

Otherwise this property returns false.

Windows that are part of an origin-keyed agent cluster are subjects to some additional restrictions, compared with windows that are not. In particular, they cannot:

• Set Document.domain, which is a legacy feature that normally allows same-site cross-origin pages to synchronously access each other's DOM.
• Send WebAssembly.Module objects to other same-site cross-origin pages via Window.postMessage().
• Send SharedArrayBuffer or WebAssembly.Memory objects to other same-site cross-origin pages.

To request that the browser assign this window to an origin-keyed agent cluster, the server must send the Origin-Agent-Cluster response header.

Note that the origin-keyed agent cluster feature is only supported in secure contexts. If a site is not a secure context, the window.originAgentCluster will always return false.

Specifications

Browser compatibility

See also

• Origin-Agent-Cluster HTTP response header
• Requesting performance isolation with the Origin-Agent-Cluster header