Every website and computer application online—or off—gathers information on its users to send back to its programmers at some point, ostensibly for feedback to improve the program. However, far more information is gleaned by social media platforms to create a profile of each user in order to target them with advertising and information tailor-made to appeal to that user and to appeal to companies and organizations that may have an interest in that user.

Facebook is upfront about this practice in the interest of serving its customers, though it keeps secret the algorithms that make it possible, and it’s important to remember that Facebook’s customers include other internet companies with things to sell to third parties, including personal information. By compiling data from user profiles and preferences based on “likes” and “shares” and following users to other web pages, Facebook creates a substantial picture of its individual users.

Ever “like” a recipe a friend posted, only to be bombarded with similar food ads on nearly every other website you visit for a month? There’s a reason for that.

Whether an unwarranted intrusion or the price of convenience (“Siri, what good restaurants are near me right now?”), Facebook and other social media companies make it possible to limit the amount of personal data they collect from individuals and provide guides on how to do so.

If someone doesn’t want a company in Silicon Valley or Beijing, for that matter, to collect and trade on their habits, like what you like to drink, where and with whom, locations and preferences, it is possible to reduce the flow of that information. Web browsers and smart phones likewise allow users to customize their search options. Third-party so-called “stealth” programs can further reduce a user’s digital footprint by somewhat obscuring the trail.

But, for the average person, the only way to stop being followed is not to log on.