The HTTP ETag (entity tag) response header is an identifier for a specific version of a resource.
It lets caches be more efficient and save bandwidth, as a web server does not need to resend a full response if the content has not changed.
Additionally, ETags help to prevent simultaneous updates of a resource from overwriting each other ("mid-air collisions")....Directives W/ Optional W/ (case-sensitive) indicates that a weak validator...changes to a wiki page (posting data), the POST request will contain...