How is Zapper’s rarity score calculated?

The NFT’s score is a normalized sum of the NFT traits rarities. This  means that to calculate our score, not only do we take into account the rarity of each trait available for a particular collection, but also how rare a particular trait is within its trait group. For example, a “blonde hair” trait will have a particular rarity within a collection, and it will have a particular rarity within the “hair” trait group of that collection.

We consider not having a trait as a trait. We also include “meta traits” into the sum, such as the trait count. Once this is calculated, the NFTs are then ranked by their rarity score within their respective collection.