Note that Feature-Policy is being depreciated for Permissions-Policy, which follows a slightly different syntax: https://scotthelme.co.uk/goodbye-feature-policy-and-hello-pe...

Content-Security-Policy is quite powerful, because it limits which origins (domains) that your page can load resources from. It can eliminate some security surprises.

https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP