Cross-origin isolation enables a web page to use powerful features such asSharedArrayBuffer. An extension can opt into cross-origin isolation byspecifying the appropriate values for thecross_origin_embedder_policy andcross_origin_opener_policy manifest keys. For example, a manifest like the followingwill opt the extension's origin into cross-origin isolation.

{"name":"CrossOriginIsolation example","manifest_version":3,"version":"1.1","cross_origin_embedder_policy":{"value":"require-corp"},"cross_origin_opener_policy":{"value":"same-origin"},...}

Opting into cross-origin isolation allows the extension to use powerful APIs like SharedArrayBuffersin its cross-origin isolated contexts. However, it does also come with certain side-effects. SeeMaking your website "cross-origin isolated" using COOP and COEP formore information on this.