High-level

Metaplex NFTs have two essential components, the on-chain metadata and the off-chain metadata. The on-chain metadata has a specification here which outlines what fields are encoded, but the most important ones are the uri (which points to the off-chain metadata) and the creators array (the set of addresses that receive royalty payments).

Anything related to the asset itself is typically in the off-chain metadata.

Technical Requirements

One requires the “update authority” to make changes to any mutable on-chain metadata.

Update authority: <your address>, is_mutable: True

• update the uri field
  • If the off-chain metadata is on S3 or behind an API, you can update the uri (and data)
    • The uri update is mainly just to provide a record of the update on chain
  • If uri is an Arweave URI, you’d need to change the link to a new JSON blob on Arweave to make changes.
• if is_mutable: False, but your metadata is in a web2 bucket that you have permission over, you can switch out the data on the S3 bucket / API directly without changing the uri, but this won’t have an on chain historical representation.

<aside> 💡 You can do bulk or bundled Arweave updates with https://docs.arweave.org/developers/tools/textury-arkb

</aside>

Upgrading an NFT

Upgrading an NFT essentially means updating the uri field to point to new off-chain metadata to reflect the new state. This can be done in a few ways:

Swaps

Burn → Mint a new one

• Can be done centralized or with a decentralized program
• Closing an NFT during the burn process allows reclamation of the initial mint cost, which can be reused for minting the next NFT; the net cost here is the cost of the 1-2 transactions (~◎0.00005 each)

Entanglement / wrapping

• Reversibly trade one NFT for another. Good for temporary events or when adding mutability to immutable constructs
  • See Transmuter for complex use-cases related to swaps / combinations

Updates

Using the latest (alpha) version of the Metaplex SDK, one can easily coordinate updates of both on-chain and off-chain metadata. See the uploadMetadata function which handles uploading JSON blobs to Arweave (or other configured storage provider) as well as updateNft which handles updating the on-chain metadata.

Technically speaking, since the JSON blob that is resolved via uri ends up determining the attributes and images related to an NFT, one could resolve that uri against any API you control. As mentioned before, this means that changes don’t get reflected on-chain, so we typically recommend at least updating the uri to reflect some change, even if the URI points to an API.