That's it, a string of letters and numbers that form a unique ID to help the site remember me.

The sites you visit do this too—that's what all those pop-ups are telling you.

Cookies actually make our online world possible.

But they also allow jeans to follow me around the Internet.

That's because cookies enable companies to band together to track and remember everything we do online.

And they've become the center of a war for our personal data.

I'm Lou Montulli.

And in the summer of 1994, I was the inventor of cookies.

In 1994, Lou was a 23-year-old working at Netscape, where they were building what would become the dominant web browser of the decade.

The broad problem I was trying to solve was to bring memory to the web.

Every time you look at a different page, that's to the web server a completely different visit.

Imagine every time you add something to your cart and click away… it disappears.

Or each time you load a new page on Facebook… you have to log in again.

Would it be fair to say that the experience of the web before cookies was a little bit like talking to Dory from "Finding Nemo"?

Yeah.

That Dory analogy is pretty apt here.

See, I suffer from short-term memory loss.

Short-term memory loss...

Cookies solved that problem.

So if in particular you were looking for a set of blue suede shoes...

With each new click, the site recognizes the unique ID from the cookie stored on my browser.

And retains information like what I put in my cart, but also often my location, what else I click on, how much time I spend there, plus details I deliberately give it, like my email address.

As I browse through the site, or even leave and come back, the cookies they added to my browser will tell them I'm the same visitor, not a different one.

Okay, so I should see that here, right? If I reload?

Yes.

Hey, wow!

Hey now, that is a lot of cookies there!

These are "first-party cookies" and over the last 20 years, they've allowed us to live more and more of our lives online.

It was really a great feeling to see people create things that we had never thought of.

But one of those things was a way to track us wherever we went next—like a news website, or social media.

The same year Lou invented cookies, this appeared: the first digital banner ad.

Today, our online world runs on ads.

The buyers in this system are brands that want to sell products by placing ads in front of people who might purchase them.

And then you have platforms and publishers with audiences of people to show ads to, like Vox.

In between, you have middlemen dedicated to making sure the ads from the brands are delivered to the right people.

Some companies play multiple roles.

Facebook and Google are the biggest players because they have huge audiences and a huge amount of information they can use to target ads to you.

All these companies are incentivized to gather as much information about your online behavior as possible.

But Lou designed cookies to be placed and retrieved only by the site you're on, so these companies are also incentivized to collaborate.

And one way they do that is with "third-party cookies."

Take another look at this list of cookies that shoe store gave me.

This one, "fbp?"

That's for Facebook, which also owns Instagram.

And this one?

That's for Google, which places ads on tons of websites, including Vox.

Now this site can go to Facebook and Google and say: "show my ads to people you know visited my site in the last month."

And there I am.

What Lou didn't anticipate in 1994 was that websites would eventually be full of elements hosted by third parties.

And those elements can save their own cookies onto my browser.

Those cookies are created by the domain of the third party, who can then access the data from the site you're on but also from every site you visit that uses those same third party elements.

This is tracking.

And it transformed our online world from one in which hundreds of companies knew a small amount about your online behavior, to one in which just a few companies can know it all.

Right now, this map of your activity is mostly used to serve you personalized ads.

But once it's collected, there's no getting it back.

In the last few years, some browsers have started to block third-party cookies by default.

Google's browser, Chrome, gives you the option if you look for it.

This makes it more difficult for the middlemen to know that the person who shopped for apartments on one site and bought medicine on another and looked for romance on another are all the same person.

But companies incentivized by billions in ad dollars will always find a loophole.

They know you don't want to block first-party cookies, because then many sites wouldn't work.

So companies like Google and Facebook can give sites a piece of code that looks like a first-party cookie, but that sends all the data to the third party anyway.

Facebook calls their solution "Facebook Pixel."

Facebook Pixel.

You can now use both first- and third-party cookies with your Facebook Pixel.

This will allow you to reach more customers and be more accurate in measurement and reporting.

And what this reads to me as is, "Don't worry, people can't turn this off.“

Well, it makes it more difficult to turn off via third-party cookies, yes.

How do you feel about the way in which companies like Facebook have used the technology that you built?

I would say that the advertising-only business model has caused products to become less good than they could be.

As long as these companies have a common goal of showing you ads for things you're likely to buy, they'll be motivated to share information with each other… about you.

And some of their new methods may be even sneakier than cookies.

I've been saying this for a long time.

There are billions if not trillions of dollars at stake and if we want to make substantial change to the methods in which tracking and advertising is done it's going to have to be done at a legislative level because otherwise we're just fighting a technological tit-for-tat war that will never end.

Especially because the companies best positioned to win that war are the tech giants that already have the most information about us, and have the most resources to find ways to get more.