The `cross_origin_opener_policy` manifest key lets extensions specify a value for the
[Cross-Origin-Opener-Policy](https://developer.mozilla.org/docs/Web/HTTP/Headers/Cross-Origin-Opener-Policy) (COOP) response header for requests to the extension's
origin. This includes the extension's service worker, popup, options page, tabs that are open to an extension resource, etc.

Together with [cross_origin_embedder_policy](https://developer.chrome.com/docs/extensions/reference/manifest/cross-origin-embedder-policy.md.txt), this key allows extensions opt into
[cross-origin isolation](https://developer.chrome.com/docs/extensions/develop/concepts/cross-origin-isolation.md.txt).

## Manifest declaration

> [!NOTE]
> **Note:** This key was introduced in Chrome 93.

The `cross_origin_opener_policy` manifest key contains an object with one
property named `value` that takes a string. Chrome uses this string as the value of the
`Cross-Origin-Opener-Policy` header when serving resources from the extension's origin. For example:

```javascript
{
    ...
    "cross_origin_opener_policy": {
      "value": "same-origin"
    },
    ...
}
```

See [Cross-origin isolation overview](https://developer.chrome.com/docs/extensions/develop/concepts/cross-origin-isolation.md.txt) for more information about this feature.