In part, to keep the internet free.
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.
Become a Patron of Ask Leo! and go ad-free!
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.
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
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
I’d be shocked if this kind of information was kept very long. Clearing your cookies3 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.
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.
Subscribe to Confident Computing! Less frustration and more confidence, solutions, answers, and tips in your inbox every week.
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.