$ERC-6220 extends the functionality of the ERC-721 standard by enabling the creation of composable NFTs. These NFTs can selectively add parts to themselves through a process called "equipping," leading to additional customization options and use cases.

Catalogs: A Catalog is a collection of parts from which an #NFT can be composed. Catalogs can contain various media types, such as images, audio, video or even mixed-media. The Catalog's type indicates the final output format when an NFT is rendered.

Equippable Parts: Parts can either be "slot types" or "fixed types." Slot types are intended for “equippables,” which allow NFT collections to be equipped into them. Fixed types, on the other hand, are full components with their metadata.

NFT creators can select parts from a Catalog and specify them for an NFT instance. Through this process, tokens can be equipped with other NFTs in their designated slots, creating a highly customizable and interactive design.

Potential Use Cases

Digital Art: Artists can create interactive digital art where collectors can personalize the art pieces by adding or removing parts directly in the art's design.

Dynamic Content: Content creators can develop uniquely tailored digital experiences, where users can customize multimedia content by equipping various categories of media, such as audio tracks, video filters or subtitles.

Token Progression: As NFT owners achieve milestones, they can equip their tokens with new parts, representing their growth and progress over time. For instance, gears can be equipped as gamers progress through the game. Another example is merit tracking, where an “equippable” NFT represents academic achievements.

Provable Digital Scarcity: Most NFTs are not truly scarce as the visual representation is a client-side mechanic. This token standard can enforce that if an item is equipped on an NFT, it cannot be equipped on another.