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Cross-Origin isolation checker

Reads COOP, COEP, CORP, their Report-Only twins and Origin-Agent-Cluster for one URL through the proxy and reports isolation readiness, stating plainly that a static header check cannot prove runtime isolation.

Press the button to read the headers

Nothing leaves this page until you do. The report grades COOP, COEP, CORP, their Report-Only twins, and Origin-Agent-Cluster on the main document, and states plainly what a static check cannot prove.

A passing result here is not a runtime guarantee. This reads the main document's response headers only. A browser grants crossOriginIsolated at runtime only when every subresource also passes its CORP or CORS check, which a header fetch cannot see. To confirm the real thing, load the page and check self.crossOriginIsolated in its own console.

HTTP header parser

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Cross-Origin isolation checker

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