NFT utilities are benefits that can be consumed by the token holders of an NFT collection. In particular, we observe two limitations in current implementations:

• There does not exist an interface for linking utilities to an NFT token on the blockchain. As a result, utility providers resort to centralised infrastructures, which do not give visibility to potential buyers on which NFT utilities are available or already consumed. Moreover, custom solutions like online forms where NFT holders fill out their digital wallet address fall sort in tracking changes in NFT ownership.
• Utilities are bound to the digital wallet that owns the NFT token. This is a constraint for various use cases compatible with delegating, reselling or subletting a utility — especially for NFT tokens that represent multiple utilities.

It should be emphasised that both limitations also pose security concerns. Centralised services are reportedly an attack vector targeting NFT collections, while NFT holders are forced to carry along and use digital wallets that might hold valuable assets.

We introduce NFZ, a toolkit for infusing NFT collections with transferable utilities, represented by on-chain tokens. NFZ tokens track ownership based on the token ids of the infused NFT collection; yet they can also be detached and transferred to a different owner or listed in a secondary marketplace. This model decouples utilities from the respective NFT tokens and can enable novel applications built around utility delegation, reselling or subletting.