Cookies. Love ’em or hate ’em, they’ve been the enabler of customer-centric digital marketing for a more than a decade now. Cookies allow you to archive previous customer behavior (such as cart and browsing data)—so long as the site visitor uses the same browser on the same device for all of their online activity.

There was a time when this caveat was a non-issue. But that time is over.

The modern customer uses multiple browser and devices every day. According to The New Multi-Screen World report published by Google, 90% of all internet users jump between multiple screens to accomplish a single task. During the purchase journey specifically, 67% of all customers begin shopping on one device and then move to another. That’s a lot of screen hopping.

So what’s the problem?

Let’s look at a typical customer journey. I’m riding the train into work when I get an email notification from the NHL website for a 10% off coupon for all VIP members. Since I’m an avid hockey fan, I click through to the mobile site right away. But my stop is next so I close Safari, exit the train, and head into work.

Later that day at work, I return to the NHL site on my laptop using Firefox. This time, I find a Philadelphia Flyers t-shirt that I’m interested in, but before I can purchase, I close my browser and run to a meeting.

At night, I get home and take out my iPad. I forget to open my email to retrieve the 10% off VIP coupon, but I complete the purchase on my iPad anyway.

Here’s the first problem: your analytics data now shows those three times that I accessed your site from three different devices, and assumes that I was three different “people.” This means you’ll only see a conversion on my iPad where I made the purchase, when in reality all three devices were involved in the purchase process.

Additionally, since I didn’t purchase the t-shirt right from the email clickthrough, you have no way of knowing that my purchase was actually the result of seeing the coupon.

Something else to consider: Experience consistency between devices doesn’t exist when you fail to connect different devices to the same person. This means that if you target an experience to me as a VIP customer, but I don’t log in or otherwise identify myself, I probably won’t be treated as a VIP.

But don’t write those cookies off as completely stale just yet.

The solution to this problem is not to ignore the IDs contained in cookies, but to connect all the ones that belong to the same person. Instead of basing your marketing strategy on disparate session data across multiple devices, why not tie together the devices that belong to the same living, breathing human and then send tailored messages to that person? Ditch the cookie-cutter one-size-fits-all experience and deliver personalization based on customers, not cookies.

The advantages of person-based marketing are considerable. You’ll be able to provide a consistent shopping experience across all of your customer’s connected devices. Plus, if you have an experience that a specific person qualifies for, they’ll see it on all of their connected devices.

Have you had success in moving towards a more person based marketing approach? Do you have questions about personalizing based on more than just cookies? Let us know on Twitter.