Technical Details

The NFToken spec is designed to be easy for non-technical people to use. If you are a creator, artist, or collector, you can create, sell, manage, and collect NFTs without needing to code.

If you are developer, it's easy to build on top of the NFToken standard to integrate NFTs into your dApp, crypto wallet, or other project. You can also extend the standard in interesting ways to add functionality to your NFT project.

Solana Overview

You can think of Solana as a large key-value database. The Solana validator nodes store the entire state of the system in memory.

Solana has a slightly different terminology than a typical key-value database. Keys are referred to as addresses and each address points at two things — a SOL balance and a data field.

Accounts on Solana

Here are three common types of accounts on Solana:

Wallets — Your wallet address points to your SOL balance. You can transfer part or all of your balance by signing an instruction that encodes the transfer.
Programs — Solana Programs are compiled into bytecode and stored on the blockchain. Validators run the code of a program by loading it from the account on chain. The NFToken program is a single program deployed at address nftokf9qcHSYkVSP3P2gUMmV6d4AwjMueXgUu43HyLL.
Data Accounts — Programs store data in different accounts on chain. An NFT is an example of a data account that is owned by the NFToken program and has data about the NFT, including who owns the NFT.

How Transactions Work

Solana uses a Proof of Stake voting system where the validator nodes add a block to the blockchain every ~ 400 ms. Each block consists of around 100 to 1,000 transactions.

Each transaction includes a series of instructions on how the validator should transform the state of the system. It could be as simple as sending SOL from one address to another address or it could be a more complex transaction that modifies the state of many addresses.

Account Schemas

The NFToken program has a few different account types:

NFT Account

NFT Accounts store the data for the NFT.

The address of the account is the ID of the NFT. This is a unique identifier.

NFT Account Attributes

authority Pubkey

When the NFT is created, the authority is set to the creator. The creator can transfer the authority to another account.

authority_can_update boolean

The authority can update metadata about the NFT if authority_can_update is true. If authority_can_update is false, then the NFT is immutable and no one can update the metadata.

holder Pubkey

This is who currently owns the NFT.

delegate Pubkey

The delegate has permission to transfer the NFT once. This is useful for selling an NFT on the marketplace. When you list your NFT on a marketplace, the marketplace program will update the delegate to an account owned by the marketplace. When the NFT is sold, the marketplace uses the delegate to fulfill the sale and transfer the NFT to the new holder.

metadata_url string

This is a string that points to a URL where the NFT metadata is stored.

collection Pubkey

This is the collection that the NFT belongs to. This is a verified field — you cannot assign an NFT to a collection without permission.

is_frozen boolean

A frozen NFT cannot be transferred. This field can be changed by the authority if the NFT has authority_can_update equal to true.

Collection Account

Collection Accounts store the data for the Collection. An NFT belongs to a collection if the nft.collection field points at the collection's address.

The address of the account is the ID of the Collection. This is a unique identifier.

Collection

authority Pubkey

When the collection is created, the authority is set to the creator.

authority_can_update boolean

The authority can update the metadata if authority_can_update is true.

metadata_url string

This is a string that points to a URL where the NFT metadata is stored.

NFT Creators Account

While an NFT can only have one authority, you may want to list multiple creators to credit people involved with the NFT and to keep track of royalties.

The creators account is a PDA so the address is derived from the seeds — ['creators', nft.address].

NFT Creators Account Data

nft Pubkey

The address of the NFT.

royalty_basis_points u16

A basis point is 1/100th of 1%. This is how much of each transaction should be paid out as a royalty to the creators.

creators Vec<NftSecondaryCreator>

The NftSecondaryCreator object has an address: Pubkey, a basis_points: u16, and a verified: bool.

When you create the NFT Creators account, the nft.has_creators field is automatically marked true.

Note that the NFToken program does not ensure that royalties will be paid out — that is up to the marketplace programs.

NFT Metadata

The current version of the spec gives each NFT and Collection a metadata_url which points to a JSON file offchain where the item's Metadata like name, image, and attributes are stored.

It's advantageous for most projects to store metadata offchain because:

It's cheaper. On Solana, storing data on chain costs money. If you only store the essential pieces on chain, creating and minting NFTs will be cheaper.
It's easier to update. If you decide that you want to update the Metadata, you can update your offchain data rather than updating all NFTs. This can be useful for some projects.
It's more flexible. Most NFToken clients will expect that your Metadata adheres to OpenSea's NFT standard (more info below), but there is no reason you can't add more data in NFTs that you create.

That being said, we are working on a version of the NFT Metadata spec that will allow NFT creators to store their Metadata on chain. This will be useful for higher value projects that want to pay more to have more data verifiable on chain.

Metadata Format

We recommend the OpenSea NFT Metadata Standard. Most wallets and NFT marketplaces will respect Metadata in that standard, so it's the most portable way to store Metadata.

Rust Docs

You can find the Rust docs here: docs.rs/nftoken/latest/nftoken