You want to reach someone.

The problem is, they consume media in more places than ever.

They watch Netflix on an iPad. They read the Washington Post on an iPhone. They use a desktop for work, but only some days, because one day a week they work from home and use their laptop.

Pretty cool for them. Not as cool if you’re a marketer trying to deliver a message to them.

And we haven’t even touched on the non-digital stuff. People listen to the radio. Look at billboards. Watch TV. Go to Giants games.

They have lives, these people! And those lives exist over many different devices and, yes, real-world experiences. Go figure.

This raises an uncomfortable question for marketers.

How do you know you’re actually talking to your best prospects, and not spending a whole bunch of money on uninterested people (or bots)?

This question is, well, terrifying. Marketers have never really been good at confronting (and answering) it.

But there is an answer to it, and it lies in a marketing buzzphrase that’s being thrown around quite a lot these days: “Identity resolution.”

Identity resolution is a data management process through which an identity is analyzed between data sets to find a match. It’s a fancy way of saying that you can match an offline persona (someone’s home address) with an online persona (their mobile habits, Google searches, what apps people use, etc.).

Identity resolution greatly improves targeting, because once you understand a person’s offline and online attributes, that person can be identified, regardless of what platform they’re using.

If you use it right, identity resolution will target your ads to real people who actually care about those ads.

They’ll be on the devices they’re using at the time they’re most likely to buy. It removes fraud, improves transparency, and leads to better performance. All this starts with real, verified people. If you’re working with a company who has that, then you’re in business.

Imagine a consumer named Amy, a 30-year-old office manager who needs a car. And wouldn’t you know it, but you’re an agency working with a big car company.

On a typical Monday, Amy’s on her iPhone in the morning, at a work computer throughout the day and on her laptop at night. With identity resolution, you can target those particular devices whenever Amy’s likely to be using them, and you can send her ads that she’d probably be interested in based on her past purchases. Oh, and you can do it when the data says she’s most likely to buy a car.

You’re more likely to win with identity resolution.

It’s certainly better than sending out ads at random, hoping to find 30-year-old professionals at random.

Identity resolution techniques analyze and confirm IDs, and prove that you’re dealing with a real person.

Apps. Email. Websites. Devices of all shapes and sizes. When customers sign off on service agreements, they agree to share their data with the service provider (we’ll get to the privacy implications of this in a second, because they’re important).

In “real life,” some data companies have access to location data, postal addresses, and point-of-sale data. Again, we’ll cover the privacy implications of this in a second.

The resulting “identity graph” provides a full look at someone’s online (and aspects of their offline) life. AI tools can then make predictions and educated guesses. For example, if someone is watching football on a smart TV in a home or a college dorm, an AI program can guess which person it is.

Three types of data are involved in identity resolution.

First-party data is the info a company collects about its own customers through cookies, email marketing lists, analytics software and so on. Second-party data comes from the brands that a company has partnered with. Third-party data originates with firms that amass and sell data about consumers.

First-party data is the most reliable and valuable type of data.

As governments enact new privacy regulations the importance of this data will only keep growing.

It’s vital to treat all this data responsibly and to be honest about how you use it. In fact, we’d venture to say that this is the most important issue facing marketers for the next, say, hundred years.

Companies must encrypt and protect the data they store, control its usage and access, and adhere to all relevant laws as well as their own terms of service. Basically: be honest with how and why you’re using people’s data. Otherwise, they’ll hate you. (But if you do this part right, they’ll love you.)

Oh, and always give them opportunities to opt out of using their data. Be transparent that if they opt out, they’re losing certain capabilities and might get served crummy ads. But it’s their data, and it’s their choice. Honesty is the only policy.

In the end, identity marketing is customized, omnichannel, timely, seamless and efficient. This is marketing-speak for “it works.” You can target your messaging across devices, and make sure it’s hitting the right people at the right times.

It also serves people ads they actually care about. As long as that data is ethically sourced — and you’re working with a data partner that’s transparent in its data uses and values the privacy and autonomy of its users above all else — it’s a win for everyone.