One of the big problems in Google Analytics’ data model is the immutability of historical data. Once a row of data is written into the data table, it is there practically for good. This is especially annoying in two cases: spam and bogus ecommerce hits. The first is a recognized issue with an open and public data collection protocol, the latter is an annoyance that can explode into full-blown sabotage (you can use the Measurement Protocol to send hundreds of huge transactions to your competitor's GA property, for example).
You might have noticed that the Referral Exclusion List in Google Analytics is difficult to maintain. You can't copy a list from one property to another, the list is a wildcard match for domain names (so all subdomains are automatically excluded), and it's just about the clunkiest user interface we've seen since ERP tools from the 1990s. A while ago, I wrote of a solution which lets you manage referral exclusions using Google Tag Manager, and it's still a neat trick, as it's way more flexible than said clunky UI.
My fingers have been tingling to write this article. Ever since I implemented Enhanced Ecommerce on my blog a couple of weeks ago, I've been getting such an impressive amount of useful data that it's mind-boggling. In this article, I'll walk you through the steps I went to implement the solution, along with examples of the data I can now access through Google Analytics’ reporting interface. As you might have guessed, if you've read my articles before, I implemented Enhanced Ecommerce with Google Tag Manager.
In this tip, we'll take a look at how to leverage a custom first-party cookie to prevent repeat hits of any kind. This is most useful for transactions, since a common problem with Google Analytics (traditional) eCommerce tracking is that a transaction hit is sent again upon subsequent entries to the receipt page, for example using the Back button of the browser. In some cases, and this is not a good practice, a receipt e-mail is sent to the user with a link back to the receipt page, where the transaction is sent over and over again upon entry.
I've noticed that setting up eCommerce in Google Tag Manager (and now the new Enhanced ecommerce) is very difficult for many. I'm sure part of the problem is that eCommerce is for many users the moment that GTM forces you to take steps in to the developer's domain, since it's obvious that you'll need to add some code to the web page. This isn't a tutorial on how to do eCommerce in Google Tag Manager.