How to display the size of a HTTP request in Fiddler?

Question

I'd like to display the size of each request in the session list of fiddler. What I tried so far, was to add a custom column in the CustomRules.js file:

public static BindUIColumn("RequestSize")
function CalcMethodCol(oS: Session)
{
  if (null != oS.requestBodyBytes)
    return oS.requestBodyBytes.Length; //this is the relevant line
  else
    return "?";
}

But this results in an error when fiddler tries to load the script.

If I change the line with the comment to this:

    return typeof(oS.requestBodyBytes.Length);

then fiddler displays 'number' in the RequestSize column. Because of that I guess that I'm not very far away from what I'm trying to achieve. I just can't figure out how to display the size of the requestBodyBytes field.

Any hints what I'm doing wrong or what is missing?

Answer 1

Update In modern versions of Fiddler, you can simply right-click the column headers, choose "Customize Columns" and add the Miscellaneous > Request Size column.

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Depending on your needs, that might not really be what you want to do, because it only shows the length of the request body, and doesn't include the size of the headers.

Here's an improved version:

public  static  BindUIColumn("Req-Size")
function  CalcReqSize(oS:  Session){        
  if (null == oS.oRequest) return String.Empty;
  var cBytesOut: int = 0;

  if (null != oS.requestBodyBytes) cBytesOut += oS.requestBodyBytes.LongLength; 
  if ((null != oS.oRequest) && (null != oS.oRequest.headers)) cBytesOut += 
  oS.oRequest.headers.ByteCount() ; 
  return cBytesOut.ToString();
}

Answer 2

OK, I knew I wasn't far off. Here's the answer to my question.

This script, when put into CustomRules.js, will print the length/size of HTTP request in fiddler:

public  static  BindUIColumn("Req-Length")
function  CalcMethodCol(oS:  Session){
    if (null != oS.oRequest)
            return oS.requestBodyBytes.LongLength.ToString();
        else
            return String.Empty;
}