The Facebook Graph API now supports HTTP ETags. ETags support on the Facebook Platform can help you reduce bandwidth consumption and client-side overhead by suppressing output when making Graph API calls.
This is how it works:
1. When you make a Graph API call, the response header includes ETag with a value that is the hash of the data returned in the API call. Pull this ETag value and use in Step-2.
2.Next time you make the same API call, include the If-None-Match request header with ETag value pulled from step-1 for this API call.
3. If the data hasn’t changed, the response status code would be 304 – Not Modified and no data is returned.
4. If the data has changed since last pull, the data is returned as usual with a new ETag. Pull the new ETag value and use for subsequent calls.