222: What is a third-party cookie, why it matters, and what to do

How do you know which part of your marketing is helping you? That’s an old problem, and over the years people have tried various methods for solving it.

Let’s say you publish “Carrot weekly” – the ultimate guide for carrot farmers. You find several sites that should attract your target audience, and you run ads on those sites. Then you create a simple marketing funnel: views, clicks, purchases.

At a simple level, you don’t know who viewed the ad, or who clicked. You can only identify the prospect when they purchase and fill out your form.

It would be so simple if people saw an ad, clicked on it, and then purchased, but that’s rare. Most people will see an ad many times before they click, and most people never click at all. But they might still buy. And they might see the ad on several different sites.

That’s somewhat frustrating. You want to attribute the sale to a specific marketing effort. That’s tough to do in the best of worlds, but it’s very hard unless you can get some intelligence on what your prospects are doing. You don’t know what they’re doing on the other guy’s site, because you don’t have analytics on that site.

If you have a customer data platform, you can track people once they come to your site. That helps answer a lot of questions about what sort of path people take before they buy, but it doesn’t answer everything.

For example, how can you track those view-through conversions – where someone sees an ad, never clicks on it, and goes on to purchase?

That’s where the third-party cookie comes in. The ad tech has a cookie on the site where you’re advertising and on your site, so the ad tech can see which visitors saw the ad on the other guy’s site and then purchased on your site. This works because there’s a single ID in that third-party cookie that follows the visitor around from site to site. Without that third-party cookie you can’t make that connection.

Or can’t you?

Let’s back up a second and talk more about cookies.

A cookie is a little piece of data that’s sent from a website and stored in the visitor’s web browser. It allows the website to keep track of the user between page views, because without the cookie, each page view would be a new, anonymous request.

A first-party cookie is a cookie that’s set by the website the visitor is on at that moment, and – this is the important part – it can only be read by that website. A third-party cookie is set by some other website – not the one the visitor is on – and it can be read by that other site. So a visitor can be on carrotweekly.com and if carrotweekly.com allows adtechcompany.com’s third-party cookie, then adtechcompany.com can see what the visitor is doing on carrotweekly.com.

That’s how adtechcompany.com can match views on one site to purchases on a different site.

If and when third-party cookies go away, that function will be much harder, but not impossible.

Imagine that 20 different farming websites decided to form a cooperative. They would all set first-party cookies, and they would all collect details about their visitors, like IP address, geographic location, browser type, screen resolution, which plugins are installed, and so on. As part of the cooperative, they’d all upload that information to a common database.

Now there’s a connection between these websites. It’s not perfect. You can’t be 100 percent sure that the information being collected maps to exactly the same user, but since when does marketing and advertising need to be 100 percent sure?

That’s one way that people are going to react to the so-called death of the 3rd party cookie. I believe Bombora is already doing this. Keep your eye on that space.

The other response to the demise of the third-party cookie is to collect a lot more first-party data. Without the third-party cookie, you can’t rely on other services to give you all that juicy marketing information you’ve relied on for so long. So start collecting your own data.

If you’re not sure how, give me a call.