You may have wondered how Facebook knows what ads to show you. Maybe you noticed that some of the ads you saw seemed to know more about you than you felt comfortable with. 

We’re here to answer the question, “How does Facebook know what ads to show me?”

The short answer is that Facebook knows a lot about you, and allows advertisers to choose what kinds of people they show their ads to. 

The long answer is really interesting, and as a professional Facebook advertiser, I can tell you a lot about how advertising on Facebook really works and what that means for you, your privacy, and your wallet.

Let’s go!

I’ll start by giving a quick overview on how advertising on Facebook works, so you can better understand what exactly is going on when you Google a new mattress once, and now your Facebook feed is full of memory foam mattress ads for the next three weeks.

How Facebook Advertising Works

Have you ever paid a subscription to use Facebook? The answer should be no, and if it’s yes, you’re probably being scammed by someone.

As of this writing, Facebook is worth over $605,000,000,000, yet it has never charged its users a fee to use the platform. Facebook makes money by allowing advertisers to pay Facebook to run ads on Instagram, Facebook, Messenger, and a few other partners across the web.

Facebook is an ideal platform for businesses to advertise on because Facebook knows a lot about its users. We’re not going to go into that here, but if you’re interested in what Facebook may know about you, check out our article What Does Facebook Know About You?

Let’s go back to the mattress example since this is exactly what’s happening to me right now.

Let’s suppose I am a memory foam mattress manufacturer. To tell customers about my new mattress, I put up billboards all over the place, pay for TV commercials, and run radio advertisements. These are working and bringing me customers, but I’m spending a lot of money to show my ads to people who aren’t interested in a new mattress. Sure, some people may become customers later, but a lot of that effort is being wasted. You may get where I’m going with this.

What if there was a way to only show my ads to people who are interested in buying a mattress right now? I’d save a lot of money on my ads, and I’d be making a lot more money since all of my ads are effective and generating more sales.

This is exactly what happens with Facebook ads.

How Advertisers Choose Who To Show Ads To

As an advertiser, I can choose who sees my ads based off of a lot of things, but here’s a shortlist of some of the options:

  1. Age
  2. Gender
  3. Location
  4. Language
  5. People’s interests
  6. If they’ve interacted with my ads before
  7. If they’ve visited my site
  8. If they’re already my customer

You can probably start to see how useful this is for businesses!  

If someone visited my mattress site but didn’t purchase, they’re much more likely to make a purchase on my site than some other random person. So what I do is tell Facebook to show my ads to only people who have visited my site but didn’t make a purchase. Then hopefully those ads will convince some of those people to come back to the site and buy a mattress.

This is how businesses seem to follow you around the internet once you visit their site once.

 Last week I visited only one mattress site, then instantly I started seeing ads from tons of mattress companies. 

How do those businesses know I’m interested in mattresses if I never visited their site?

This is where Facebook’s “Interests” come in.

Facebook Thinks It Knows What You’re Interested In

Based off of all of your activity on Facebook and other sites that share data with Facebook, Facebook tries to figure out what you’re interested in, then shows you ads based on those “interests”.

Sometimes Facebook is really good at figuring out what you’re interested in, but sometimes they’re pretty bad at it.

If you want to see what Facebook thinks your interests are, go read our article, What Does Facebook Know About You? and follow the instructions to see all of the interests Facebook thinks you have. It’s very entertaining to see how many interests they get terribly wrong.

Anyway, now that I’ve visited one mattress site, Facebook may tag me as being “Interested in mattresses”. Now I’ll start seeing the ads from all of the advertisers who are showing ads to the people interested in mattresses.

Within a few weeks, maybe after I’ve bought a mattress and I am no longer visiting mattress sites, watching mattress review videos, and clicking on mattress ads, Facebook decides that I am no longer “Interested in mattresses”. And just like that my mattress ads stop showing up.

As a quick note, Facebook doesn’t let advertisers know the identities of the people who they’re showing their ads to.

As a professional Facebook advertiser myself, I’ll tell you that this example is a simple explanation of how Facebook knows what ads to show you, but it’s enough for you to understand how it works.

If you’re curious about why Facebook is showing you a specific ad, you can actually find out why you’re seeing it. Here’s how:

  1. When you see an ad on Facebook, click or tap on the ellipses (…) in the top right corner.
  2. Then click or tap Why am I seeing this ad?
Facebook Why Am I Seeing This Ad

This page will show you some of the reasons why you saw that specific ad. From this page you can manage or change some of your Facebook ads preferences, though it’s smart to understand exactly what you’re doing before you start changing your ad preferences. Check out our other articles about Facebook ad preferences so you can better personalize your ad experience on Facebook.

By now you should understand how ads on Facebook are necessary to Facebook continuing to be a free tool and how advertisers use Facebook to show you ads that can feel like they know too much about your, and sometimes prove that they hardly know you at all. A fun game to play is to try to get Facebook to show you ads about something you’re really not interested in.

Good luck!