Can You Be Anonymous Online?
Internet services, such as websites, have to know how to find you in order to share information with your individual computer or device. Websites are like the postal service: if they’re going to deliver a package, they need to know your address—and they’ll probably learn a lot about the neighborhood from their visit. All of this information about how you use online services can be tracked and stored, either by the site or service you're using or by a third party such as an advertising service that feeds ads to a website. Different websites can also automatically compare their data to determine whether you've visited both.
Even if your devices don't give you away, people (or data mining algorithms) may be able to find similarities between your online activities on different accounts that give away that you're the same person. For example, more advanced technologies like facial recognition are becoming common and automatic on social media platforms (e.g., when you upload photos), and other methods like voice recognition and analysis of your writing style are available as well.
Therefore, there is no such thing as true anonymity on the Internet. Anytime you do anything on the Internet, you leave evidence of your identity and activities, commonly known as the digital or information footprint—even if you never give out so much as your name.
Tracking and Online Advertising
There are a number of methods currently used for tracking online activities. One of the most common methods of tracking is through "cookies", small text files that are stored on your computer or mobile device by the website you visit—or by a third party that displays content or ads on that site. Especially in the latter case, cookies often track your activities across different websites. Even if you delete old cookies and don't accept new ones, there are other ways of tracking you. Websites and online advertisers may be able to figure out who you are from other evidence, including your device's IP address (its unique numerical identifier, something like 127.0.0.1). In addition, each device's web browser has a specific configuration (including information like version number, screen resolution, and operating system). Your device shares this information with websites so they can display information and images correctly. However, each device's configuration is fairly unique, creating a "fingerprint" that can be used to identify you.
Tracking has a number of purposes. It analyzes how you use use a site or service, and often makes using online services more convenient. For example, if a website tracks when you are logged in, it doesn't have to ask for your username and password each time you navigate to another page. Ad providers track your online activities to determine which ads they should display to you. In behavioral advertising, advertising services use data about your web browsing history—often gathered across multiple sites—to build a profile and infer what you might be interested in buying. This may include direct information about your interests, like the fact that you searched for "sippy cups", or information guessed from those interests, like your probable age. As a result, you may find that looking at sippy cups means you’ll be seeing ads for baby products even when you go to an astronomy website.
Many businesses and organizations are able to offer free services because of the profit they make from selling your information to advertisers—but this shared data does include a lot of information that could potentially be used to identify you. Not all tracking is bad, but it depends on factors like who is tracking you, what information is collected, who is using this information, for how long is it stored, etc.
People are always looking for ways to avoid tracking, and many anti-tracking technologies are effective for a while. But tracking technology is always changing, as companies find new ways to track your valuable data. If you're concerned by online tracking, use the tips in your privacy toolkit to find effective tools, but remember they may go out of date. In addition, no method is foolproof; if someone is knowledgeable enough about the technology, they may still figure out who you are.
In some cases, people may have misconceptions about what privacy-enhancing technologies actually do. For example, checking the "Do Not Track" option in your web browser's settings means websites will be notified that you don't want to be tracked—but in practice, most sites ignore this request. Similarly, "private browsing" and "incognito" modes can prevent the next person who uses your computer from seeing your web browsing history, but they do little to prevent websites and services from tracking your online activities.