The lazyload feature policy allows developers to selectively control the lazyload attribute on <iframe> and <img> using the Feature-Policy header or the <iframe> "allow" attribute. This provides more control over loading delay for embedded contents and images on a per origin basis. Use this policy to force loading to delayed or non-delayed for your entire website and all or parts of any embedded contents. Use of this policy benefits page load times.
The policy will be removed in favor of a newer feature policy for loading, namely loading-frame-default-eager which is more aligned with how the "loading" attribute will be used.
Docs: https://github.com/w3c/webappsec-feature-policy/issues/193