Cross Device Tracking - MGR Blog

As the cookie weakens, brands and agencies are looking for an alternative. Cross-device seems to be the answer – but questions remain. In this article, AdExchanger examines the state-of-play around cross-device IDs.

Consumers are media multitaskers – and cookies are not.

As users migrate to mobile at record speeds – according to comScore, apps already account for more than 50% of time spent on digital media – advertisers and publishers are starting to recognize the promise, and the many challenges, associated with cross-device targeting.

Cross-device technology as a subset of the overall ad tech industry only became truly relevant when smartphone and tablet adoption hit their stride around 2010 and 2011. It became clear that the ability to match users across their various devices would provide brands with an unprecedented targeting and data-collection opportunity.

Until relatively recently, cross-device identification primarily meant linking desktop computers, tablets and smartphones. With the advent of connected TVs, wearables and the Internet of Things, the concept of cross-device is expanding to potentially include anything that gives off a signal.

Some vendors paint an encouraging picture, touting the many potential upsides of their cross-device analytics solutions, including the ability to extend desktop segments to mobile, improve measurement and attribution and roll out sequential messaging across multiple screens depending on a user’s particular journey.

But it’s still early days, and there are plenty of barriers.

Can cookies cut it on mobile?

Data is the fuel that makes digital advertising go and cookies are its dominant tracking vehicle. The advertising industry has leaned heavily on cookies ever since they hit the web in the mid-90s.

Basic retargeting is what most consumers think of when they hear the term “cookie,” but ad networks, ad exchanges, demand-side platforms and sell-side platforms continue to depend on cookies to serve the targeted ads that form the cornerstone of their businesses.

Arguably a flawed mechanism on desktop, cookies are positively crippled when it comes to mobile.

Although cookies do exist on mobile – it’s a widely held misconception that they don’t – the fact is that they’re both unreliable in the mobile web browser environment and all but neutered on the app front. The problem with cookies on the mobile web is that they reset every time users close their browser. The problem with in-app cookies is that they can’t be shared between apps, rendering them essentially useless.

That’s why two other tracking methods, probabilistic matching and deterministic (logged-in user data) have become the cross-device coins of the realm.

What’s the difference between deterministic and probabilistic matching?

There are two ways to establish user identity across devices, one far more exact – and therefore potentially more problematic from a privacy perspective – than the other.

The deterministic method relies on personally identifiable information (PII) to make device matches when a person uses the same email address to log into an app and a website, thereby creating cross-device linkage. As long as a user is logged in across devices, advertisers and publishers can use this unique identifier to target those users on multiple screens with near-perfect precision.

This tactic requires scale in order to be effective, which means it’s mostly reserved for giants like Facebook, Twitter, Google, Amazon and Apple, all of which have enormous user bases and maintain mobile and desktop properties that require logins.

Probabilistic cross-device matching is achieved by algorithmically analyzing thousands of different anonymous data points – device type, operating system, location data associated with bid requests, time of day and a host of others – to create statistical, aka likely, matches between devices. For example, if a phone, a tablet and a laptop connect to the same networks or Wi-Fi hotspots in the same places every weekday, it’s safe to surmise that all three devices belong to a specific commuter. But it’s not an exact science.

Although deterministic matching seems like the “better” solution, users don’t always stay logged in or use the same email address everywhere. And although a player like Facebook has an impressively high percentage of mobile-only users – overall desktop usage is down on Facebook, a fact that might diminish its ability to create cross-device matches down the line as future users eschew desktop for mobile.

What about attribution?

Multi-touch attribution, the process by which advertisers determine the impact of their ad spend across touch points, is still in its infancy. However, what is very clear is that if you’re still using ‘last click’ attribution to track your ROI, you are missing the big picture.  The truth is that the road from a first impression to a final purchasing action is becoming more and more twisted every day making it very challenging for companies and ad agencies to accurately measure the ROI of their marketing budget. To that end, Google says it wants to rid marketers of their obsession with the last click before consumers buy things. Instead it aims to provide insights about how earlier ad dollars perform in areas like TV, digital video, store visits and search.  As noted in our previous article, last click attribution will very soon become a thing of the past.


This is always a fascinating subject for me and our MGR SEM Team and we spend quite a bit of time discussing it too.  To me, as a marketing professional that is paid to spend other people’s money, the important thing is to never lose sight of the end result; that is, increase our customers’ revenues month-after-month and quarter-after-quarter.  We can split the marketing pie any way we want, gather all sorts of customers’ data, attribute conversions one way or another, get lots of website visitors, and on and on.  But if all of that does not translate into increased revenues, it will just be a ‘feel good, look good’ exercise and a monumental waste of time.

What are your thoughts?  Feel free to comment below or simply, send me an email with your ideas.  As always, thank you for reading.  Until next time, this is Manuel Gil del Real (MGR).

Sources: -Allison Schiff;,