HTMLFencedFrameElement: allow property

The allow property of the HTMLFencedFrameElement gets and sets the value of the corresponding <fencedframe> allow attribute, which represents a Permissions Policy applied to the content when it is first embedded.

Not all permissions policies are allowed in fenced frames. The allowed permissions are listed at Permissions policies available to fenced frames — these are required for fenced frame content originating from the specified APIs to load. If you don't set the allow attribute, those permissions will be allowed by default. If you want to narrow down the permissions set, you need to make sure that all of the required permissions for the APIs you are using are set in the allow attribute.

const frame = document.createElement("fencedframe");
console.log(frame.allow);