bytesIn bytesOut objectSize

How are these metrics defined?


bytesIn and bytesOut are the number of bytes sent on the wire for a given request (including headers, compression, etc).

objectSize is the size of the actual “thing” returned (payload) without the http headers.

Hmmmm. The page request returns an objectSize of 0. Why would that be? bytesIn is non-zero.

Do you have a sample result?



It seems to be the page request itself. So for example from the test history:

2010/11/16 12:45:10	New York, NY - IE8 - DSL

The request to has an objectSize of 0.

My initial thought was that since is a 301 redirect to you could get a 0 byte response, but WebPagetest usually handles redirects with no problem (e.g. or Can you provide a link to the actual test result?

Ah, ok, interesting.

Take for example, the raw object data for this result.

The page request has a response code of 0, bytesIn > 0, objectSize=0.
Requests with response code of 302 or 204 have bytesIn > 0, objectSize=0.
Some requests with response code of 200 have bytesIn =0, objectSize=0.
A couple of requests have bytesIn=0, objectSize=-54.

Sorry, are you looking at the raw data? If so you need to watch out for the “Transaction Type” column. The only requests that actually went on the wire are requests of type 3.

Transaction Type 0 is some summary stats for the overall page
Transaction Type 8 is for requests that were served from the browser cache (fairly recent addition to track these)