"transferred over network" size larger than resource size

Question

I am using XMLHttpRequest to read the json file and find that "transferred over network" is significantly larger than the resource size.

xmlhttp.open("GET", "resources.json", true);

While others have resource size equal to or larger than "transferred over network". What happened to it? Should I be worried about this?

Answer 1

Transfered is the total amount of bytes traveled in both directions, while resource size is the size of received response body.

A HTTP request is composite of url, request headers, request body, response headers and response body.

See a sample message of a HTTP request:

POST / HTTP/1.1
Host: foo.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 13

say=Hi&to=Mom

Note that the content length header is only 13 bytes (only the say=Hi&to=Mom size),while this entire HTTP message contains 111 bytes.

For more details see the message format section at https://en.m.wikipedia.org/wiki/Hypertext_Transfer_Protocol