They don't worry me, but others feel differently.
In two other articles -- What Can a Website I Visit Tell About Me? and What Are Browser Cookies and How Are They Used? -- I discussed how websites gather information about the people who visit them.
What I didn't talk about in much detail is that through clever use of cookies -- typically associated with advertising -- some services gather and use more information about you.
We need to talk about tracking and third-party cookies.
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Tracking cookies
Cookies are pieces of data stored on your computer by websites to remember information between visits. Third-party cookies, often used by advertising services, track your behavior across multiple websites. While this enables targeted advertising, individual users aren't personally tracked, and data is analyzed only in aggregate.
Cookies 101
First, a quick review: a cookie is just some data placed on your computer when you visit a website. That data is sent back to that website the next time you visit it.
That's all.
When you visit askleo.com, for example, the website might place a cookie on your machine that says "This person has seen the newsletter pop-up." A week later, when you visit askleo.com again, that cookie is automatically and transparently sent to the website so it knows you've already seen the newsletter pop-up and it won't annoy you with it again.
That's all cookies are: a way for websites to remember things between visits. What they remember is completely up to what the website chooses to place in the cookies it leaves on your machine.1 They can contain pretty much anything.2
Next, we need to talk about how most advertising works on a website.
Advertising 101
Most advertising on the internet is performed by services connecting large numbers of advertisers with large numbers of websites signed up to display ads.
So when you visit https://example.com, you might see ads from https://ads.somerandomservice.com. (To be clear, all URLs here are fictitious examples.) Later, when you visit some other site -- maybe https://reallybigbookstore.com -- you might see ads there from that same advertising service: https://ads.somerandomservice.com. When your browser loads the page from https://example.com, the HTML on that page says, in effect, "Place an image here. Get that image from https://ads.somerandomservice.com/..." at which point your browser dutifully goes out to ads.somerandomservice.com and gets the image, which is an ad.
This is where cookies enter the picture.
Cookies + Advertising = Third-Party
When your browser fetches a URL -- be it the page you asked for or an element within that page, like an ad -- the website it contacts can place cookies on your machine.
So when you go to https://example.com, then of course example.com can place cookies. However, if that page also references another website (like https://ads.somerandomservice.com/) for an image on that page, then ads.somerandomservice.com can place cookies as well.
These are called third-party cookies.
- You are the first party.
- The site you visit is the second party (example.com in our example).
- The site(s) referenced for additional content by the site you visit are third parties (ads.somerandomservice.com in our example).
So far, so good; you visit a site, it can place cookies, and the sites that provide additional content on that page can also place cookies.
Here's where it gets interesting.
Let's walk through a scenario step by step.
- You visit example.com.
- Example.com has ads that are loaded from ads.somerandomservice.com.
- The first time you visit example.com, ads.somerandomservice.com puts a cookie on your machine that says, "This is advertising visitor #12,345,678."
- Now you go visit reallybigbookstore.com.
- Reallybigbookstore.com happens to use the same ad service, ads.somerandomservice.com.
- Ads.somerandomservice.com already has a cookie on your machine. When the request is made to display an ad, that cookie is sent to ads.somerandomservice.com.
- Ads.somerandomservice.com sees the cookie it put down earlier that said, "This is advertising visitor #12,345,678."
- Ads.somerandomservice.com now knows that you -- advertising visitor #12,345,678 -- visited both example.com and reallybigbookstore.com.
That is a tracking cookie at work. Third parties use cookies to understand where you go on the net within the sites they service.
It gets bigger
So far, all I've talked about is advertising services. In reality, this simple technology can and does span more services.
For example, you may have heard of a company called Google. They have their fingers in many, many pies.
- Advertising - Adwords for advertisers, Adsense for websites who want to make money from ads
- Analytics - Google Analytics, a comprehensive analysis tool that allows websites to understand how people use their site
- Personal productivity - Gmail, Contacts, Calendar, and more
- Cloud services - Google Drive, photo sharing, YouTube, and more
- Personal publishing services - Blogger
The list goes on.
The net result is that by interacting directly with a Google service or interacting with a site that uses a Google service3, you are exposed to many opportunities for Google to leave tracking cookies on your machine.
It's not just Google; they're just a large, easy-to-understand, somewhat extreme example. The same is true for varying degrees of other advertising networks and behind-the-scenes online service providers.
Blocking third-party cookies
Most browsers block third-party cookies by default. It seems like this would invalidate much of what I've listed above. Sadly, that's often not the case.
When third-party cookie blocking on the rise, advertisers and other services have developed other approaches. Tracking still happens via cookies, so-called ever-cookies, local storage, on-page information, and more. It's more complex, for sure, but not that difficult.
That's why you'll sometimes see ads that "follow" you around the internet even if you have third-party cookies disabled.
Who cares?
My fervent belief is this:
Your actions as an individual are completely uninteresting. No one cares.
No one is tracking you personally. Besides, most of these services collect way too much data to drill down to any one person.
Instead, this type of tracking is examined in aggregate. For example, with this data, the advertiser can determine things like "40% of people who visit example.com also visit reallybigbookstore.com." None of them say or care that "Leo Notenboom visited both example.com and reallybigbookstore.com."
At best, they can say, "Anyone who visited example.com and looked at X should then be shown ads for X when they visit reallybigbookstore.com." Note that it's "anyone" -- generic, anonymous people -- and not "Leo Notenboom".
Advertisers and website owners eat that stuff up. They use it to make decisions that support their profitability.
But, again, I strongly believe that Leo Notenboom just isn't that interesting as an individual.
And don't take this personally, but neither are you.
Do this
Don't sweat cookies or other targeted advertising. I know it can feel creepy, but I strongly believe they're not looking at you as an individual but rather as anonymous people who behave in specific ways.
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Footnotes & References
1: Exactly where cookies are stored varies from browser to browser, but CTRL+SHIFT+Del is a common keystroke to bring up the dialog that allows you to clean them.
2: While cookies can contain anything, because of the way they're used, it doesn't matter what they contain. They can't harm your computer.
3: Like Ask Leo!, which uses Google services.
I really am not concerned about being tracked, rather I prefer not to have any distractions taking up my screen space.
That is why I use Privacy Badger, uBlock Origin and DuckDuckGo Privacy Essentials. Firefox is my default browser and Privacy & Security is set to Standard. When I visit a webpage, what appears on my screen is the main content and little else.
There are a few websites that I do whitelist to support the owners and I’m willing to put up with the ads. The browser is set to clear the browsing history and cookies when I exit, except for websites that I log into, such as Ask Leo!
Another thing people worry about is cookies taking up space. I never cleart cookies and I checks the space occupied. They are taking up about 100 MB, about 0.00001% my 1 TB drive. It’s not worth worrying about.
Re: “I never clear cookies.”
A ptetty meaningless statement. Let’s make it clearer: What is the date of your oldest web cookie?
I don’t know and I don’t care.
I use Firefox as my default web browser on both Windows and GNU/Linux. I use the default security settings (standard) that came with it, and I haven’t noticed anything out of the ordinary. As an individual user, I’m not very concerned about cookies in general, and tracking cookies fall into that category. That’s mostly because, as Leo says, I don’t think I’m all that interesting, so I see no reason why anyone would waste the time to track me specifically.
Anyway, my activity on the Internet’s probably not of much use to advertisers. Most of my time on the Internet’s spent trying to learn about whatever project/adventure I’m embarking on at the moment. When I want to purchase something, I do my research, and select the item that best suites my needs within my chosen price range. I never make impulse purchases, and I’m more interested in the results of my research than any advertisements I may see online. When I consider purchasing a device I’m unfamiliar with, my first step is to learn about it, and which features/characteristics make one model better than another, as well as which specifications to look for. As an example, screen refresh rate, and default resolution matter when choosing a display/monitor.
Ernie
“When I want to purchase something, I do my research, and select the item that best suites my needs within my chosen price range.” The results of your research can be influenced by tracking. That’s why I use Duck Duck Go search. The results of tracking can be subtle.
Why I Stopped Using Google Search
i use a program called superantispyware to clear my cookies weekly
All browsers have a setting to clear history on exiting. You can have it clear browsing and download history, the browser cache, and/or cookies, and more. That is similar to using your browser in private or incognito mode.
That reminds me of an article I read in one of my trade journals. Some shopping websites will list a different price than someone else for the same item. If you visit 3 websites for the same item, a 4th website for the same item might be cheaper for you than someone else because a cookie “sees” you visited a competitor for the same item. Likewise, if you go back to abc.com, the price could be higher because it “sees” you saw an exact item at other websites where the price was higher. Instead of the original $19.95 on abc.com, it is now $23.95 because the other websites had the item as $26.95.
Hmmm. For my posting above, I clicked on reply for “Mark Jacobs (Team Leo) October 1, 2024 at 1:30 pm”, but my reply is appearing at the bottom of all the postings instead of immediately following Mark’s posting.