Tracking users on the Internet | Internet safety | Khan Academy

So there's a bunch of reasons why a website might want to track you, and depending on your opinion, you might think some of these are reasonable and you might think some of them are unreasonable. Just to understand, imagine if you were to go to, say, Khan Academy, and you were to do some work. Well, it might be nice that if you were to come back another day, that that work isn't lost. And so that might be a reason why you would want Khan Academy to know who you are.

Now, there's a bunch of different ways that this could happen. The most obvious way is by having an account with a username and a password. So when you type in your username and password, the site knows exactly who you are. It can retrieve your data from a database, and then you can pick up right where you left off. That's probably the most obvious to people, and it's also the most obvious how to not be tracked in that way is that you log out.

But just because you logged out, or just because you don't have a username and password, doesn't mean that you can't be tracked by a site. There are several other ways that can be tracked that you should know about and also know how to undo them if possible. Another way is leveraging something called cookies. Cookies, even if you don't have an account on a site, most web browsers are going to allow the website to place a little bit of text on your computer.

So the browser, which is running on your computer, is going to place it so that next time your browser goes to that site again, the site will say, "Okay, this is the same person whose cookie I put there." Then that cookie might have a little bit of data associated with it and say, "Okay, there could be some useful things we can pick up where we left off. We can customize for what you're looking for." Or you might say, "That's a little bit creepy that a site that I didn't give permission to is able to keep track of me."

And so you might want to delete your cookies, which your browser will allow you to do. Now cookies, as I said, they have their benefits. This is one of the reasons why you can often stay logged in to a website because the website says, "Oh, this is a cookie. This is the person who keeps logging in." You might want the personalization of the advertisements or any other customizations without logging in, and that's where a cookie could be useful. But if you don't want it, of course, you can delete it.

Now, another way that a website can keep track is your IP address. When your web browser, which is running on your computer or on your phone, wants to look at a website, it sends a request to that website. Then that request sends the data, sending the website back. And so, in order to send the data back, it needs an address for your phone or for your computer, and that's going to be in the form of an IP address.

Now, you can imagine if that site knows your IP address, and then if you were to come from the same device with the same IP address again, it'll say, "Okay, it's at least the same device. Maybe it's the same person." And then they might be able to track you in that way. Once again, it might be for some good uses, like customization, or maybe it's things that you aren't so comfortable with.

Now, what gets extra interesting and might be useful or not useful, depending on your point of view, is that it’s not necessarily just your relationship with one website. For example, you might have an advertiser that puts cookies on a bunch of websites and can keep track of you as you go from site to site. And so then it's getting, at least for me, I don't like the fact that people can see how I'm moving around on the internet.

I remember recently I was looking for a mountain bike, and I did it on one e-commerce site, and then all of a sudden it seemed like the whole internet knew that I wanted to buy a mountain bike. I didn't end up buying a mountain bike. Now, some of you might say, "That's nice. You know the internet knows I want a mountain bike. I'd like to keep being presented with ads on mountain bikes." Some of you might say, "Hey, that's not so cool. I was just, well, you know, a random search I did, and it’s kind of weird that the internet is starting to build this profile of me of someone who might be in the market for mountain bikes."

And so, once again, deleting your cookies can go a long way to preventing that type of thing if you're uncomfortable with it. And then IP addresses, that's a little bit harder to hide. Sometimes you have dynamic IP addresses, sometimes it changes, but the clearest way of protecting your IP address is if you use something like a virtual private network, which does get a little bit more complex.

Now related to all of this, some of you also might be thinking about being tracked when you do a search. You might see that, "Hey, these suggested searches that the site is giving seem like they're kind of specific to me," and that's because, in many cases, it is. The search engine probably has placed cookies or it's keeping track with an IP address of things that you have searched for before and the things that you have clicked on.

And so it could use that maybe to give you different search results, maybe to change what the autocomplete is. It also might be keeping track of a search history. So the search history could be useful if you want to look at other sites that you have been to before, or you might not want that around. You might not want the, you might not want the site or someone else, who if you just happen to be using your computer, to see what you've been searching for.

So most browsers, sorry, most search engines are going to let you delete that. So there’s a lot more to it. This is just kind of the tip of the iceberg. But think about how you may or may not be tracked, and think about how you may or may not want to be tracked. Good hygiene is especially important if you're at a public computer: log out of things—that's also so other people can't use your account. Really be thoughtful about whether you even want to create an account for a site. Is this something that you really need? What are going to be the benefits for you?

Think about whether you want to accept cookies. I would recommend deleting cookies pretty regularly. It might have some negatives; you might have to re-log into a few sites, but there's probably a lot of other shady sites that no longer can track what you're doing. But even if you do all of those things, still be very careful and very conscientious.