Cross-device targeting (or tracking) is a way to link different sessions from the same visitor on your website. The idea is simple: people may visit at different times, and on different devices. Cross-device targeting lets you tie the visits together, so that you recognize the same person regardless of the device being used.

When visitors can be tracked across devices, marketers can target them with personalized offers. This makes remarketing a powerful tool. If you don’t link desktop and mobile sessions in this way, you essentially lose customers when they close their laptops. Marketers miss out on opportunities to connect with them, and find it more difficult to understand their journey.

Two key approaches to cross-device targeting

There are two ways to approach cross-device targeting. The first is deterministic targeting, when a user has to sign in to get full functionality. This is also referred to as first-party tracking. Using this method, there’s no doubt that the right users are being identified, because they’ve provided the data we need to follow them. While you need to convince the user to cooperate by opting in and signing up, you’ll be rewarded with 100 per cent accuracy, provided that person logs in.

The second method is probabilistic targeting, which is far more complicated. It involves making a best guess that the customer is the same person by crunching huge amounts of data to find patterns of usage. Despite the fact that you need massive amounts of data, this method is surprisingly accurate, identifying people with over 97 per cent accuracy. The issue here is that users don’t necessarily know that they are being tracked.

Is cross-device targeting worth the investment?

Gartner estimates that 4.9 billion devices will be used to connect to the internet this year. In many cases, one user will have access to multiple devices and will browse to the same destinations on all of them. From desktop computers to smart watches, each device is a candidate for cross-device targeting because it fills in a blank for marketers.

The technique offers huge benefits in terms of reducing wasted impressions, and it can help achieve more effective audience engagement and attribution. Right now, only 3 in 10 marketers are using cross-device targeting, according to an eMarketer survey.

When it comes to collecting data about customers’ actions, mobile is particularly problematic. Cross-device targeting offers a unique chance to recapture individuals on their mobile devices.

Caveats and next steps

We briefly mentioned the privacy implications around user tracking, and it’s important that markers have an ethical approach when working with personal data. Right now, there is no unique identifier that can reliably track someone, but it’s likely that tracking technology will get better over time.

Additionally, smaller companies may find it more difficult to use cross-device targeting, because they cannot tap into valuable data streams that larger businesses have come to rely on. According to Econsultancy, one-third of publishers in North America currently don’t have enough data to act on. It’s quite common for providers to restrict access to their data, which puts everyone else in the market at a disadvantage. As we try to refine our understanding of consumer behavior, first party tracking will be the new battleground for marketers.