How rarity works
Every ranked item on rare has a rarity rank inside its collection. Rank 1 is the rarest. We compute the ranks ourselves from the traits of every item in the collection.
The score
For each trait an item has, we take how often that value appears in the collection. A value held by 1 in 100 items has a frequency of 1%. The item's score is the sum of 1 divided by the frequency of each of its traits.
score = sum of (items in the collection / items with this value), over every trait type
If an item has no value for a trait type that other items have, it counts as having the value None for that type. Missing a trait most items have is itself rare.
The rank
Items are sorted by score, highest first. Items with the same score share a rank, and the next rank skips ahead (1, 1, 3).
What we count
We count every item we know for the collection, listed or not. Burned items are left out. Trait names are matched without case or extra spaces, and numbers by value, so 1 and 1.0 are the same value.
When ranks change
Ranks are recomputed a few minutes after the collection changes: new items are minted, items are burned, or traits change. A rank can move when that happens.
Unranked items
Items without traits get no rank. A collection needs at least two items with traits to be ranked. When we cannot rank a collection from traits and another marketplace publishes a full ranking for it, we show that ranking instead.
Tiers
The tier label comes from where the rank sits among the ranked items: Mythic is the top 1%, Legendary the top 5%, Epic the top 15%, Rare the top 35%, Uncommon the top 60%, and Common the rest.