Pull metadata from ERC721 contracts

Question

what tools/services would you recommend for pulling metadata from ERC721 contracts? It seems like it's going to be a huge hassle to return the metadata directly from the blockchain. Any clever ideas?

Answer 1

Alchemy now has the query getNFTMetadata. Here is an example response it returns:

{
  "contract": {
    "address": "0x34d85c9cdeb23fa97cb08333b511ac86e1c4e258"
  },
  "id": {
    "tokenId": "3",
    "tokenMetadata": {
      "tokenType": "ERC721"
    }
  },
  "title": "",
  "description": "",
  "tokenUri": {
    "raw": "https://api.otherside.xyz/lands/3",
    "gateway": "https://api.otherside.xyz/lands/3"
  },
  "media": [
    {
      "raw": "https://assets.otherside.xyz/otherdeeds/54abf723d8b4a7a885753fd4345b8d182f590ab150f7c9778d0a320b27b134bd.jpg",
      "gateway": "https://res.cloudinary.com/alchemyapi/image/upload/mainnet/51f809642d9c5d15861b56dbf07f66b1.jpg",
      "thumbnail": "https://res.cloudinary.com/alchemyapi/image/upload/w_256,h_256/mainnet/51f809642d9c5d15861b56dbf07f66b1.jpg",
      "format": "jpg",
      "bytes": 957484
    }
  ],
  "metadata": {
    "image": "https://assets.otherside.xyz/otherdeeds/54abf723d8b4a7a885753fd4345b8d182f590ab150f7c9778d0a320b27b134bd.jpg",
    "attributes": [
      {
        "value": "Harsh",
        "trait_type": "Category"
      },
      {
        "value": "Biogenic Swamp",
        "trait_type": "Sediment"
      },
      {
        "display_type": "number",
        "value": 2,
        "trait_type": "Sediment Tier"
      },
      {
        "value": "Splinter",
        "trait_type": "Environment"
      },
      {
        "display_type": "number",
        "value": 4,
        "trait_type": "Environment Tier"
      },
      {
        "value": "Spikeweed",
        "trait_type": "Eastern Resource"
      },
      {
        "display_type": "number",
        "value": 3,
        "trait_type": "Eastern Resource Tier"
      },
      {
        "value": "Whisper",
        "trait_type": "Southern Resource"
      },
      {
        "display_type": "number",
        "value": 3,
        "trait_type": "Southern Resource Tier"
      },
      {
        "display_type": "number",
        "value": 3,
        "trait_type": "Plot"
      },
      {
        "value": "First Trip",
        "trait_type": "Obelisk Piece"
      }
    ]
  },
  "timeLastUpdated": "2022-08-31T15:40:43.391Z",
  "contractMetadata": {
    "name": "Otherdeed",
    "symbol": "OTHR",
    "totalSupply": "100000",
    "tokenType": "ERC721"
  }
}

Answer 2

You need to return some information from the blockchain, otherwise nobody can know which source is authoritative.

Typically, people set up the contract to return URLs. (ERC-721 allows URIs, a superset of URLs).

Here is one such URL for the Su Squares contract: https://tenthousandsu.com/erc721/00050.json

And accordingly, that is the URI for the Su Square token with tokenId = 50.

You can query those URLs from the blockchain using JavaScript Web3.

Answer 3

I think this question is not correct because "metadata" is not actually stored in the blockchain but a URI to the metadata itself; So the real question is:

Q: How to read the URI from the token?

• A: You will need a Ethereum

  RPC Node provider with APIS that read it from the blockchain for you. There are several providers with free tiers that can fulfill your development requirements

Moralis Infura Alchemy. <-- someone answered getNFTMetadata which is a valid answer

As an extra info that might help to better understand this question is, "how does it work?"

Mint: When you mint a token in any NFT Contract, either ERC721 or ERC1155, the smart contract generates a new token with a unique id, stores the ID and then transfers it to the buyer's wallet

Metadata: Contracts have a function that returns the right URI according to a preset "base prefix" (can be a ipfs endpoint or a webserver); to read this you just need the "smart contract address" and "token id"

Example of the metadata function:

const prefix = "www.someendpoint.com/";
const anotherprefix = "ipfs:/"; //if the metadata is hosted in ipfs

function uri(uint256 tokenId)
    public
    view
    override()
    returns (string memory)
    {
        return string(
            abi.encodePacked(
               prefix + tokenId
            )
        );
    }