AdWords Conversion Linker: What is it and why do you need it?

This is related to an email AdWords sent out at the beginning of September regarding the upcoming Safari update which introduces the Intelligent Tracking Prevention (ITP).

The new technology intends to improve people’s privacy by using machine learning to determine which domains can track people across sites. It works by limiting tracking for the allowed domains by only letting cookies act in a third-party context for 24 hours. This article will explain what the Adwords Conversion Linker is, why it came about, and how you can implement it to avoid losing out on essential data.

To better understand the issue Google is trying to solve and also why you need to implement the new Conversion Linker we first need to cover a basic understanding of how cookies work.

Cookies and how they work

A cookie, besides any other data it contains (name, expiration date, content etc.), would always contain the domain it has been written for. Below is an example of a google advertising cookie:

The cookie can only communicate the data it holds (for example, whether a user has clicked a link) to the domain it has been written for. Therefore, the above cookie can only communicate its contents to googleadservices.com.

If you are visiting Bill’s Shoe Website, then a cookie written for www.billsshoewebsite.com would be considered a first-party cookie.

If there is a cookie on www.billsshoewebsite.com which sends data to another website (e.g. a Facebook like button sending data to Facebook.com, then it is considered a third-party cookie.

Note: Cookies are not intrinsically first or third party – this is decided by the browser at runtime.

How does this relate to AdWords?

Let’s get back to our AdWords tracking point, and the point of this article.

To date, AdWords cookies have always been third-party cookies (since they send data from any domain to www.googleadservices.com).

Safari and Firefox are taking steps to block third-party cookies (to varying levels). By default this means that often people converting on these browsers aren’t tracked by the regular AdWords conversion tag. This is bound to only get worse with the coming ITP update to Safari mentioned in the beginning of the article.

In essence, it means that essential AdWords conversion data is becoming lost, as it cannot be tracked from these browsers.

Sometime in September, Google announced a new AdWords conversion tracking option which replaces the www.googleadservices.com cookie with an additional Google Analytics cookie. That is significant because the GA cookies are written against the domain they are tracking. Essentially, this circumvents the above limitation as these cookies will now be considered a first-party cookie on your website.

The new Google Tag Manager (GTM) Conversion Linker tag works in a similar way. It simply reads any Google Click Identifier (GCLID) and Urchin Tracking Module (UTM) URL parameters relating to AdWords clicks, and sets them in a cookie on your own domain. Then later, if a conversion occurs, it can be properly tracked, even in browsers that block third-party cookies.

Both these options would allow you to track users of browsers that block third=party cookies by default, as well as users that have chosen to block these cookies. Considering the ease of implementation of the new Conversion Linker tag it’s a no-brainer if you have GTM and use an AdWords conversion pixel currently.

Note: You only need to do this if you haven’t linked your Google Analytics with AdWords (more information: https://support.google.com/adwords/answer/7521212?hl=en-GB )