How Does Facebook Determine Interests For Ads Targeting?

When targeting Facebook ads to interest audiences, it’s not always clear to advertisers how Facebook determines these interests. This article lifts the curtain.

Facebook determines interests for ads targeting using a variety of sources both inside the Facebook platform as well as on external websites that have the Facebook pixel installed. These include: profile information, content someone engaged with, groups, page likes, visited websites and more.

Facebook interests are often confused with Facebook page likes.

Many advertisers think that Facebook determines interests purely based on the Facebook pages a user likes. That’s incorrect. And it’s just one of the misconceptions about how Facebook determines the interests you can target…

The Sources And Data Points Facebook Uses To Determine Interests

Facebook is a social platform. But above all it’s a data-company, that collects insane amounts of information about their users’ behavior and preferences.

To do that, they use a variety of different sources. From within their own ecosystem (Facebook, Messenger, WhatsApp, Instagram). And from outside of it through the Facebook pixel that’s installed on millions of websites as well as through partnerships with 3rd-party data providers.

These enormous amounts of data points, allow Facebook to determine interests based on behavior and not just self-defined profile information.

Amongst other things they use:

  • Profile information
  • Content someone engages with (both on and off-platform)
  • Page likes
  • Groups someone is a member of
  • Purchase behavior (through the Facebook pixel)
  • Websites visited

Advertisers need to realize that it’s in Facebook’s interest to increase the size of interest audiences, because they generate revenue by providing targeted ad placements to advertisers.

More reach = more revenue 💸 (for Facebook, not necessarily for you…)

3 Common Misconceptions About Interests As Determined By Facebook

The past few years I’ve been selling InterestExplorer, a tool that reveals targetable interests that are not pre-populated in Facebook Ads Manager.

I’ve literally answered 1000’s of questions about Facebook interests, which gave me insight into the common misconceptions advertisers have about Facebook interests and how they are determined.

These are the 3 most common ones I hear a lot:

Facebook Interests Are Equal To Page Likes

Facebook interests are determined based on more than just the people that like the eponymous Facebook page.

For example, take a look at the number of people that like Mailchimp’s Facebook page (403,939) or the people that follow it’s updates (465,796).

mailchimpe facebook page

While if you add the MailChimp interest to Facebook Ads Manager, it shows you that the (worldwide) interest audience includes 1,956,550 people.

mailchimp facebook interest

And if you add the same MailChimp interest to Facebook Ads Manager, it estimates an ever bigger audience of 2M – 2.5M people.

mailchimp facebook audience insights

Maybe you also noticed that the name of the Facebook page is written slightly different than the interest audience (Mailchimp vs. MailChimp).

The people who like the Mailchimp Facebook page are part of the MailChimp interest audience, but they’re not the same thing.

People Who Facebook Determines To Have A Certain Interest, Are Actually Interested

As mentioned earlier in this article, Facebook determines interests not just based on self-defined information but also on assumes interests based on user behavior. Including engagement with content.

That means that a comment on a friends’ post about her new cat, might Facebook lead to think that YOU are interested in these furry creatures.

That might not be the case at all.

The best way to understand how far-off Facebook can be when determining interests, is by looking at what Facebook thinks are YOUR interests.

You can do that by visiting the Ad Preferences, which Facebook created as a response to the growing demand for transparency about their ad platform.

Here you can see a list of all the topics Facebook has determined that you’re interested in. Like the my “interests” in the screenshot below.

facebook interests in ad preferences

The most interesting one to me is “Fortune-telling”, which I’m don’t even have the slightest bit of interest in. Still Facebook has determined I have this interest so I’m part the 13,170,450 people “Fortune-telling” audience.

facebook interest fortune telling

Makes me wonder how many others in that audience also aren’t interested in that topic (and thus are a waste of advertising budget).

Facebook heavily inflates the audience size for any given interest, and so interest audiences include many people that aren’t interested at all.

Having A Facebook Interest Means, Wanting To Buy A Related Product

The fine-grained targeting options on Facebook have given advertisers the impression that it is very easy to reach the right people.

But then they often ignore the fact that having an interest does not mean that you belong to the target group that wants to buy a product that is related to that interest. Let alone, now.

Don’t get me wrong, interests are a great way to define your target audience. And also to exclude people that don’t belong to that audience.

It’s just that for some audiences, interests are more defining than for others.

Let me give you an example.

When you sell dog care products, you’re probably looking to target dog owners. Dog owners are an audience of people that often like Facebook pages related to their specific breed. Maybe they’re even part of certain Facebook groups where owners of the same breed discuss their pet.

chihuahua interest

If you’re a dog owner, you can be clearly defined by interests. And these interests will remain stable across many years,.

The same goes for hobbies or passions.

When you have a webshop that sells crochet products, you’re looking to target people for whom crochet is a passion that they spend of lot of time (and money on). These people can also defined by their shared interest in certain pages, groups and content they engage with.

crochet interest

See what I mean?

Contrary to these types of stable and passionate audiences, there are audiences that are harder to target when you rely just on interests.

When you are a realtor and you’re trying to sell houses, almost anyone can be part of your audience at some point in their lives. But timing is probably more important than interests.

I mean if you target an audience of people that have interests related to “real estate”, you’ll probably target othe realtors or real estate investors.

Not necessarily people who are in the market to buy a home.

housing interest

How To Use Facebook Determined Interests For Your Targeting?

It’s important to be aware of the common misconceptions about how Facebook determines interests, when you’re using interest-based ad targeting. As you now know, it’s not as easy as it seems.

Some target audiences are easily defined by the interests that Facebook determines based on page likes, groups and content engagement.

While other interests are less defining, or sensitive to the right timing.

And then also take into consideration that Facebook is not always accurate often wrong when determining the interests of users.


If you’re new to this topic, I highly recommend you read my free Definitive Guide On Facebook Interest Targeting to learn more about finding, selecting, testing and scaling Facebook interest-based campaigns.

You can also quickly scan the article I’ve written about the full list of Facebook interests that’s available to advertisers.