How do advertisers find users on a second device and why do they care?

Sam Barnett is the CEO and co-founder of Struq.

According to research by Time Warner, users switch between devices an average of 27 times a day. For any advertiser that wants to target you with relevant advertising this is a massive issue and, through necessity, the advertising industry has evolved. We no longer perceive the user population as just a set of separate devices but rather many users with many devices.

The key is knowing which user owns which device; but how does it work and why do advertisers care?

Quality vs quantity – deterministic vs probabilistic matching

The first thing to know is that there are two main techniques for matching a user to their devices; deterministic and probabilistic.

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Deterministic matching achieves a 100 percent accurate matching rate through the use of user logins. In short you log into your favourite Web-based service on your desktop and your smartphone and an advertiser will then know that those two devices belong to you.

Obviously this approach relies heavily on the user logging in. On average an advertiser will achieve a match 60 percent of the time with 100 percent accuracy (please, no Anchorman quotes). It is that 100 percent accuracy that means advertisers will often look for retargeting providers with the necessary publisher relationships to achieve a good spread.

Probabilistic, as the name suggests, operates on a statistical approach. It uses factors such as the specific device details and location to match the user to the device. This approach, often referred to as fingerprinting, provides nowhere near the 100 percent accuracy of deterministic but does allow advertisers to match without a user login.

So it truly is quality vs quantity. Many advertisers will baulk at probabilistic because of its lack of accuracy but will not have the means to match using the deterministic method. The best bet is to find a provider with a good publisher network. The best providers will augment deterministic matching with probabilistic methods to lift match rate and ensure the best reach for a campaign. There are many reasons to go to all this effort, most important though, are brand safety and relevance.

Bad advertising could destroy your brand image

Using a deterministic approach can protect your brand against the negatives of retargeting. By using matching to target across devices you ensure that a user sees relevant ads on every device. Serving ads for a product the user already bought is a surefire way to create a bad experience.

The most common cause of this is when a user browses for the same product on their desktop and mobile. If they then convert on their desktop, and the advertiser is not matching them across devices, chances are they will still get retargeted for that product on their mobile. These ads are obviously eye catching but in the worst kind of way and will lead to a loss of trust in the brand.

Personalized messaging increases brand familiarity and revenues

While it is easy to stand out in a negative way, gaining a positive reaction from a user (a purchase) is far more difficult, especially in the saturated online advertising space. Advertisers are finding that being able to present a uniform message in their advertising across devices means a significant rise in sales and a drop in advertising cost.

The ability to serve a user an ad that, not only contains the exact or similar products that they have browsed, but also relevant marketing messaging based on where they are in their purchase journey, raises user engagement.

Advertisers need to understand the roles of different devices

The relevance of this messaging increases if an advertiser has a proper understanding of why their user is on a specific device. For example; 81 percent of smartphone shopping is spur of the moment [PDF], with click through rates 50 percent higher and conversion rates 50 percent lower than desktop.

Matching allows an advertiser to create a uniform view of the user. What they browse on their mobile can dictate what adverts are served on their desktop and vice versa. Without these solutions, advertisers are wasting time and money on ads that, at best aren’t relevant, and at worst are detrimental to their brand.

Now that users are switching devices so regularly, advertisers need to keep pace and move with them if they wish to keep enjoying the benefits of personalized advertising.

Don’t miss: 3 tools to help protect your brand while retargeting

Image credit: Shutterstock