Why Do Ads Follow Me Around the Internet?

In part, to keep the internet free.

Advertising networks notice what interests you. It might be a little creepy, but it's not malware.

A cartoon-style image of a surprised person sitting in front of their computer. The computer screen is overflowing with colorful pop-up ads, each showing products that the person has recently viewed online, like electronics, books, and clothing. The person's expression is exaggerated with wide eyes and a dropped jaw, capturing their shock and confusion about the nature of these targeted ads. The setting is a quirky home office with a vibrant desk, a fun, stylized chair, and playful decorative items in the background. — (Image: DALL-E 3)

Question: After visiting major online computer and electronic retailers’ websites, I find that they have tracked items I looked at, combined with my computer’s browser settings or web address and then displayed these items as pop-up ads in my other browser pages. I believe something from the computer store website has inserted spyware into my browser settings, and I refuse to trust any spyware. If I increase the security settings, many sites I need to visit no longer function. I have pop-up blocking enabled and expensive anti-virus working, but this is circumvented. I can individually block the sites, but how or what can remove their new spyware from my computer?

Let me put your mind at ease: this is not spyware, and it’s not malicious.

It may be a little creepy, but there’s no intent other than marketing.

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Ads that follow you

A technique called remarketing allows advertisers to show ads for things you’ve previously looked at.

The technique targets your computer, not you as an individual.
Clearing cookies periodically or using an ad blocker may help.
Ads that seem to follow you are benign and nothing to be concerned about.

Remarketing

What you are seeing is an advertising technique called remarketing. It’s used by advertising networks, which are companies websites contract with to present the advertisements you see. Most ads on Ask Leo!, for example, are provided by an advertising network.1

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#2032

It works like this.

You visit a shopping site or a site that offers some kind of service. This site may or may not show ads, but they do include content, such as trackers, from an advertising network.
The advertising network places a cookie on your computer. That cookie contains information to the effect of, “This computer was looking at X,” where X is the product or service offered by the site you’re visiting.
Eventually, you move on to another website — a site that also displays ads and, coincidentally, uses the same advertising network as the site you started at.

That advertising network is given its own cookie back — the one that says, “This computer was looking at X” — and as a result, elects to show you ads for X.

There are several variations, and I’m sure the implementation is more complex than I’ve outlined above. With so-called “third-party cookies” (which is what these are) on the decline, other techniques are being developed to the same end.

As a concrete example, I frequently visit the website of the company that hosts my websites to manage the server. I often see ads for that company as I move on to other sites on the internet. The advertising network has no way of knowing that I am already a customer.

Advertising and tracking

I get that it feels a little like someone is following you. It’s like you visited a jewelry store and as soon as you left, someone started following you, pestering you to purchase from that store. “I know you’re interested because you came into the store and looked at this ring. Here it is again. Are you sure you don’t want to buy it?”

Technically, this type of tracking isn’t tracking you as an individual; it’s just a side effect of the places your computer has visited. Any computer that happens to view product X will likely see ads for X as they visit other sites.

So it’s your computer, not you personally, that this happens to. Move to a different computer, and you might see a different set of ads. If you don’t, it’s because your activity on that second computer was similar to that on the first — i.e., you looked at X on both, and thus will see ads for X on both.2

Practical implications

I’d be shocked if this kind of information was kept very long. Clearing your cookies 3 will likely cause the remarketing system to forget what your computer has seen and begin the process again.

It’s certainly not spyware, and it’s definitely not malicious software on your machine. It’s simply advertisers leveraging how the internet and web browsers work by showing you ads for things you’ve shown an interest in.

Do this

There’s nothing much you can do about this without using an ad-blocking solution.

I know it makes some people uncomfortable, and understandably so, but ultimately, there’s nothing to be concerned about here.

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Footnotes & References

1: Except for ads I place manually — typically for my own books and services.

2: Technically, it’s even more granular than that. Since cookies are kept separately for each browser, it’s generally enough to switch to a different browser to see different ads.

3: Beware: depending on how you clear cookies, this technique can include side effects like getting logged out of all the sites to which you are currently logged in.

5 comments on “Why Do Ads Follow Me Around the Internet?”

Jai

May 25, 2020 at 7:49 am

Hello,

I am looking to add this ‘feature’ to a website (ad of the products on my site on external sites). I am no developer or technical person. How can I go about adding this cookie on my site?

Thanks,
Jai
- Leo Notenboom
  
  May 25, 2020 at 9:08 am
  
  I’m afraid that’s well beyond the scope of what I can provide here. It’s complex, and generally involves working with an ad network.
  - Jai
    
    May 26, 2020 at 8:54 am
    
    I see! Thanks, Leo. Just for my information so that I can check this n’network’ better, can you share some information on any one such network that may be ‘easiest’ to work with?
    - Leo Notenboom
      
      May 26, 2020 at 12:42 pm
      
      Google’s Adwords is the most popular as I understand it.
aa1234aa

February 27, 2024 at 12:19 pm

Ads don’t have to follow you. All it takes is a little effort.
Don’t use Edge or Chrome for a browser (you have no real control).
Firefox browser is somewhat better. Go through all browser settings to configure it the way you want. In Firefox, learn all about what you can do with “about:config”.
Set the browser to clear cookies when you close the browser.
Set the browser to clear history when you close the browser.
Set the browser not to accept 3rd party cookies.
Turn off (disable) any setting that talks about “suggesting” or “referring” or “a better experience”.
Turn off any browser “autofill” feature because it remembers what you did.
Turn off any “secure DNS” feature because it tracks sites you visit.
Don’t be logged into any account, such as Gmail, while you’re browsing to shop.
For any shopping or browsing session restart your browser (assuming you have configured it up to clear cookies and history when closing).
Websites cross-share cookies (i.e. pass info between them), so if you’re shopping on site A don’t have tabs open on site B.
Go to one site at a time and clear cookies between them.

Of course, the bottom line is that you believe and trust that you’re browser settings actually do what they claim and they are not just a “feel good” front.

If you really mean business, learn all about modifying the hosts file (in Windows) to block out certain websites.