How to track per visit referrer with Google Analytics

Prevously I wrote about how traffic sources in Google Analytics perhaps aren’t what you think, mainly due to GA’s attribution of page views, visits & visitors to the latest source. It’s not possible using out-of-the-box Google Analytics for you to see the full referring page for each individual visit.

Use Custom Variables

It is possible to use a custom filter to see the full referrer, but it’s also possible to collect the URL of the referring site by making use of custom variables and a bit of javascript. With the same technique you can also store the search phrase for those visits that came via a search engine result page.

The technique described below isn’t 100% accurate, (some situations cause the referring URL not to be passed on; such as opening links in new windows in Chrome) but then many aspects of Google Analytics aren’t 100% so I don’t think I’m leading you astray.

Step one: add _setCustomVar lines to your tracking code

Will Critchlow’s post describing how to implement first touch tracking article inspired me into using custom variables to record the referrer URL of each visit as well as any associated keywords.

I re-wrote the _setCustomVar lines in his code to use the new asynchronous format. What this following piece of code does is to send the referring URL and keywords to Google if a referrer exists. If no referrer is present it sends “Direct”, so we can track all direct visits too. the “2” at the end of each setCustomVar tells Google Analytics that it’s a visit level variable.

It also filters out your own domain, so that your data doesn’t get polluted by people following internal links from one page to another.

This “if” statement need to be placed in your code after the _setAccount and before the _trackPageview.

var refurl = document.referrer;

  if (refurl != '')
  {
   if ((refurl.indexOf("://"+document.domain))<0)
   {
     _gaq.push(['_setCustomVar', 1, 'Ref', 
        truncate(refurl.substr(7,refurl.length)), 2]);
     _gaq.push(['_setCustomVar', 2, 'Qry', 
        getkeywords(), 2]);
    }
  }
    else
  {
    _gaq.push(['_setCustomVar',1,'Ref','Direct', 2]);
    _gaq.push(['_setCustomVar',2,'Qry','', 2]);
  }

Step 2: Truncate just in case

As Will mentions in his article, Google Analytics limits the length of the data you can send
(including the variable name) to 64 characters – or rather, it ignores anything bigger. So I borrowed his truncate function. I’ve altered it so that we can use three-character variable names (I thought that single character variable names was a little too cryptic for my use)

function truncate(input) {
  var byteLength = 61;
  return decodeURIComponent(encodeURIComponent(input)
.substr(0,byteLength));
}

Step 3: Setting the query parameter

As there isn’t a standard parameter for the search query across all search engines, I needed to make a function that could deal with the major ones that used something other than “&q=”. I saved a bit of time by looking at a php function for displaying the referring page. It’s obviously no problem to add more conditions to catch other search engines if your site receives traffic from one that isn’t captured correctly.

function getkeywords() {
  var x = document.referrer;
  var keywords = 0;
  if (x.search(/yahoo/) != -1) {
    keywords = gup("p"); 
  }
  else if (x.search(/digg/) != -1) {
    keywords = gup("s"); 
  }
  else {
    keywords = gup("q"); 
  }
  keywords = truncate(keywords.replace(/+/g, " "));
  return keywords; 
}

Step 4: Extracting the keywords

In Will’s original First Touch post, he saved the query string unaltered with no tidying up or further parsing. I adapted the code from this article that parses the URL of the current page so that it parses the contents of document.referrer. At the time of writing, Google Analytics has a bug in it which means custom variables get spaces displayed as %20 in reports.

This is the routine that the getkeywords function above calls once we’ve worked out the query parameter.

function gup(name) {
  name = name.replace(/[[]/,"\[").replace(/[]]/,"\]");
  var regexS = "[\?&]"+name+"=([^&#]*)";
  var regex = new RegExp( regexS );
  var results = regex.exec( document.referrer );
  if( results == null )
    return "";
  else
    return results[1];
}

Sit back and wait

After a few hours you’ll be able to find some results via custom reports (and perhaps “Visitors -> User defined”) but it can take a few days before results show up under the Custom Variables report.

Once they do start to appear, you should see something similar to that in the picture below.

Now you are collecting referrer information on a per visit basis, including if the visit is direct – as well as all the associated search queries. It should also be relatively straight forward extend this technique to track other per visit information too, but we’ll save that for another day…

Updated: 2011-01-17

I’ve updated the code above to take into account situations when the refering URL is your own domain.