Identify individual consumers engaging across multiple devices.

Picture this: you’re at work on a Friday afternoon right before a holiday weekend, passing time with a little online shopping on your computer. (Don’t worry – we’ve all done it.) Five o’clock rolls around, and as you’re walking to your car you receive an ad on your mobile device from your favorite store with a 30% off holiday weekend coupon. You hop in the car and swing by the store on your way home from work, eager to find a discounted outfit for the upcoming holiday festivities.

With cross-device tracking, companies now have the power to do just this.

As the power of cookies weakens and digital users increasingly turn to mobile, cross-device tracking is becoming more and more important.

Back-up – what’s an internet cookie?

On a high level, cookies are small files that a website collects containing data about a user’s visit. Browsers save the cookies for the future to remember things like what the user put in their shopping cart, or their name, address, and phone number previously used on a form to make a purchase.

With internet cookies, consumers have the opportunity to opt-out of being tracked. Though consumers may prefer this for privacy purposes, it makes the task of sending on-target and relevant messages even more difficult for advertisers.

Mobile cookies are….. crumby.

Cookies are still very relevant to desktop, but in a digital environment rapidly becoming dominated by mobile, cookies are less helpful to developers, brands, and advertisers. This is because on the mobile web, cookies reset every time users close their browser. Additionally, on mobile apps, cookies are not shared cross-app.

Thus, when solely relying on cookies, developers, brands, and advertisers are essentially seeing the same digital user as three different people when tracking them via desktop, app, and mobile web.

There is clearly room to optimize customer experience by recognizing these “three” users as the one person that they make up.

Sounds simple enough, but how do you do it?

There’s a rapidly emerging concept termed “cross-device ID tracking.” Essentially, cross-device tracking is the process of collecting and combining data in a way that links all devices used by one person back to him or her.

Cross-device tracking is imperative because it allows advertisers to see if the ad served via mobile resulted in a desktop purchase, or visa versa. It also allows you to track user behavior on all devices to serve proper ads and content where it will be most effective.

There are two different types of cross-device tracking: deterministic and probabilistic tracking.

Deterministic Device ID Tracking:

Deterministic tracking involves recognizing personally identifiable information (PII), like an email address, when it is used across multiple devices to log into apps and websites. The deterministic method of device ID tracking is typically seen as more accurate than the probabilistic method.

When a user logs into Facebook on their desktop, and the Facebook mobile app on their cell phone, deterministic tracking will understand this user as one person. As long as the user stays logged in, advertisers will be able to target him with custom content where he will consume media.

With the use of PII, precision is almost perfect. This is because deterministic tracking relies on known data. Whether it’s an email address, home address, phone number, or credit card number, there is no guessing involved.

It sounds so simple, right? You’re probably thinking, “why isn’t everyone using deterministic device ID tracking?”

Well, deterministic ID tracking requires the kind of scale that only the big wigs, like Google, Apple, Facebook, and Twitter have. You need a lot of data, and these companies all require users to submit login information to access their accounts. It’s more difficult for smaller companies to implement this process.

Probabilistic Device ID Tracking:

As an alternative to deterministic device ID tracking, probabilistic cross-device tracking relies on algorithms…. a lot of them. The probabilistic method tracks billions of anonymous data points from a bunch of different elements tied to digital use.

Elements include, but are not limited to:

• Screen resolution
• Device type
• Operating system
• Location
• Wifi network
• Behavioral/browsing data

Remember – these are anonymous data points. In other words, probabilistic tracking differs from deterministic tracking because the data points do not contain personally identifiable information.

All the data points are fed into an algorithm that spits out a probable unique user across each device.

If that’s still confusing, let’s break it down. Say you’re connected to your wi-fi at home with your desktop computer. A few hours later, you’re connected to that same wi-fi from your mobile device. It can be deemed probable, in conjunction with a ton of other data points, that the devices belong to someone in that household.

Thus, probabilistic device ID tracking is less accurate than deterministic tracking. It is better at tying a device to a unique household than to a unique individual.

This doesn’t seem like such a big deal, right? Wrong. Let’s say, for instance, your boyfriend is researching engagement rings on the desktop computer in your shared apartment. If probabilistic device ID tracking goes wrong, you could be served an ad for a big diamond ring on your mobile device in that same household a few days later. This situation is less than ideal.

The probabilistic method is more scalable for smaller companies, but less accurate than deterministic data.

The Power of Cross-Device ID Tracking is Clear

Both types of cross-device tracking carry their own set of strengths and weaknesses. However, it’s clear that as the industry becomes more and more mobile dominated, advertisers are coining new ways to keep up.

Now, it’s easy to understand how desktop online shopping Friday afternoon led to an immediate mobile ad from your favorite store that holiday weekend, right?

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