Welcome to the second article of our marketing attribution deep dive series. In this series of blog posts I walk you through everything there is to know about marketing attribution from high level concepts to the nitty gritty technical details.

Marketing attribution is the practice of evaluating the marketing touchpoints a consumer encounters on their path to purchase. The goal of attribution is determining which channels and messages impacted the decision to convert or take the desired next step.

The first step in marketing attribution is to track the customer journey.

The customer journey is the complete sum of experiences that customers go through when interacting with your brand and purchasing your product. It’s a roadmap that traces each touchpoint where customers come into contact with your company, from awareness to consideration, to decision, and finally, to retention.

An example of this would be a customer clicking on a Facebook Ad and visiting your website on Monday. Then on Wednesday the same customer clicks on a Google Ad and visits your store again, this time browsing several products and adding on to their cart. Then on Friday they get an abandoned cart email, clicks on the email, visits your website and makes a product. This whole journey from Facebook Ad to purchase is the customer journey.

The most common way for attribution platforms to track customer journeys is to use something called a tracking pixel.

A tracking pixel is a piece of html code embedded into a webpage. When a user visits the page, the tracking pixel loads, sending information back to a server about the user's activity. This data can include IP address, operating system, browser type, and interactions with the webpage.

You are probably familiar with some common tracking pixels. The Facebook pixel, Google Tag manager, and TikTok pixel, are all tracking pixels.

Historically tracking pixels were implemented as very simple html image tags that load a 1x1 invisible image on the page. Hence the name “pixel”. Nowadays tracking pixels are generally script tags that use javascript to function.

An HTML image tracking pixel:

<img src="https://example.com/tracking-pixel.png" alt="" width="1" height="1" />

A javascript tracking pixel:

<script>
  (function() {
    var pixel = new Image(1, 1);
    pixel.src = "https://example.com/tracking-pixel.gif";
  })();
</script>

Tracking pixels are essential tools for monitoring customer journeys from start to finish. Here's how they work: an e-commerce store installs a tracking pixel on its website. When a customer visits the site, the tracking pixel fires and records information about the visit. This data includes the page the customer visited, the timestamp of the visit, the web browser they used, and any actions taken on the page, such as adding items to the shopping cart. As the customer returns to the website over the following days and weeks, the tracking pixel continues to log these visits.

The key piece of this whole process is assigning a unique identifier to each customer. This unique identifier is used to stitch together the customer's journey such that each visit can be tied back to the correct customer. Your average e-commerce store will have thousands of customers visiting per day, without a unique identifier for each customer, it would be impossible to construct unique customer journeys for each person.

There are several ways of assigning unique identifiers to a customer. Modern attribution platforms will use multiple identifiers in tandem as a robust and fault tolerant way of keeping track of customer identity. Three of the main identification methods are cookies, fingerprinting and ip address matching.

A cookie is a small piece of data stored on a user's web browser by a website. These text files contain information that the website can read and use during subsequent visits by the user. Cookies are a fundamental part of the web, helping to improve user experience by remembering information about the user, their preferences, and their activities. The reason that cookies are needed is that HTTP (the protocol that is used to transmit web pages) is a stateless protocol, meaning that state is not kept from one website visit to the next. Cookies are a way to maintain state between subsequent website visits so that you can stay logged in to a website, keep items in your shopping cart, etc.

Cookies are one of the many ways a unique identifier is assigned to a customer by a tracking pixel. Typically the way this works is when a customer first visits a website the tracking pixel generates a random id string like “ec69b961-8517-4a4a-aae2-d9180c4bbabc” and stores that id in a cookie on the customer's web browser. This cookie can then be read by the tracking pixel on future visits to the website and the customer journey can be constructed.

Cookies are the most well known methods to store text data on a user's web browser but modern browsers also have other methods to do this known as local storage and session storage. These generally behave similarly to cookies and modern attribution platforms will use them alongside cookies to store the unique identifier.

There are pros and cons to using cookies to store unique identifiers. One pro is that it is a simple and reliable way to uniquely identify a user. Only one user will ever have the unique identifier stored in their cookie so failure modes like identity collision are completely avoided. In addition to that, all modern browsers support cookies which makes it a reliable technology to depend on. Some of the cons to using cookies are that they can be deleted and blocked in various ways which can cause the unique identifier stored in them to be lost. Cookies can be lost by a user manually clearing them. Cookies can also be blocked by an array of different browser plugins and browser privacy technologies like Apple's ITP. These will be discussed in more detail in a future article.

Fingerprinting is a sophisticated web tracking technology that collects information about a user's device and browser configuration to create a unique identifier, or "fingerprint." Unlike cookies, which store data on a user's device and can be easily deleted, fingerprinting gathers details such as screen resolution, installed fonts, operating system, browser type, and even subtle hardware differences. Fingerprinting is powerful because it provides a way to track users without relying on stored data on their devices, making it more robust and reliable in certain circumstances.

The way fingerprinting is used to track a customer journey is similar to the way cookies are used. When a customer first visits a website the tracking pixel will generate a fingerprint for that customer. Every subsequent visit from that customer from the same browser will have the same fingerprint and thus the customer journey can be constructed.

Over long time periods fingerprinting can be less reliable than cookies because a user's fingerprint will naturally change over time as they update their browser version, update operating system version, install new browser plugins, etc. This is why in practice fingerprinting is generally used in tandem with cookie tracking.

Tracking the customer journey is a foundational step in effective marketing attribution. By understanding the full scope of a customer's interactions with your brand, from initial awareness to final purchase, you can make informed decisions about where to allocate your marketing resources. Utilizing tools like tracking pixels, cookies, and fingerprinting helps create a detailed map of customer behavior, providing valuable insights into which channels and messages drive conversions.

In this article, we've explored how tracking pixels function as a cornerstone of this process, capturing vital data about user visits and actions. We've also delved into the roles of cookies and fingerprinting in uniquely identifying customers and piecing together their journeys. Each method has its strengths and challenges, but when used in combination, they offer a robust framework for accurate and comprehensive marketing attribution.

As we continue this series, we'll dive deeper into other aspects of marketing attribution, including advanced techniques and best practices to enhance your marketing strategy. Stay tuned for more insights and practical tips to master the art and science of marketing attribution.