InterestExplorer is a smart application to discover interests that you can target on Facebook, but that are hidden in the Facebook Ads Manager (which only shows 25 interest suggestions).
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How to use the Facebook Marketing API to reveal 1000's of interests that are hidden in the Facebook...The FB Ads Manager suggests only 25 interest suggestions to target. Don't use these because you'll face heavy competition and high CPC's. Research with Facebook Audience Insights or via Google is limited and often returns interests that cannot be targeted in the FB Ads Manager.