Charles Proxy to Analyze Ad Calls

Charles

Charles is a web debugging proxy tool which can record or analyze the HTTP (or HTTPS) calls going from your PC to internet. This is a basic Charles proxy tutorial. Few of the other famous free ones are… Fiddler, Wireshark & Burp which are equally good. We are using Charles proxy here and you may use any other tools you feel comfortable with.

What do they do and why here?

These tools act as an intermediary, capturing the traffic going from browser to internet and back. In ad serving, it help us in breaking down the ad requests that the browser send to Double Click Ad Server and the response DFP server sends back.

Lets dive in

Lets start this Charles proxy tutorial with GPT here.

Request Area

If you are using GPT tags on your page then the requests will be sent under http://pubads.g.doubleclick.net in gampad.

The Google GPT(Google Publisher Tags) ad request will be a GET request having multiple parameters like for eg. prev_iu_szswhich shows the ad request sizes, iu_parts showing the ad unit name etc.

correlator : It’s used in cache busting and is auto generated by DFP JS libraries. For ad requests coming from a single page, the correlator value must be same. You may check out regarding cache busting in DFP on this page.

iu_parts :  Shows the network ID followed by the ad unit name or the hierarchy in case of a child ad unit.

prev_iu_szs : The ad request sizes. In SRA, you can see multiple ad request sizes separated by comma. 

scp : The slot level targeting key value pairs. 

cust_params : Page level targeting key-value pairs. .

Response Area

The ad requests response can be seen under the response tab and it will list the results that DFP returned to the browser. Let’s check out what surprise it holds in store for us.

DFP ad response parameters:

Google-LineItem-Id : ID of the winning Line Item and multiple IDs if its an SRA(Single Request Architecture) ad request.

Google-Creative-Id : The winning DFP creative ID from that Line Item and multiple IDs if its an SRA.

When nothing’s going right & everything’s a mess…:

Google-LineItem-Id  is -1 : Tells that DFP returned an AdSense or AdExchange line item.

Google-LineItem-Id  is -2 : Means DFP didn’t return an ad a.k.a an Unfilled Impression. The ad selection process didn’t return a Line Item.

Here is the Video Tutorial: