By providing asset metadata, applications like NFTify can bring in rich data for digital assets and display them in-app. Digital assets on a given smart contract are typically represented solely by a unique identifier (e.g., the token_id in ERC721), so metadata allows these assets to have additional properties, such as a name, description, date, and image.

1. Implementing Token URI

For NFTify to pull in off-chain metadata for ERC721 and ERC1155 assets, your contract will need to return a URI where we can find the metadata. To find this URI, we use the tokenURI method in ERC721 and the uri method in ERC1155. First, let's look at the tokenURI method in a contract.

/** 
   * @dev Returns an URI for a given token ID 
   */ 
  function tokenURI(uint256 _tokenId) public view returns (string) { 
    return Strings.strConcat( 
        baseTokenURI(), 
        Strings.uint2str(_tokenId) 
    ); 
  }

The tokenURI function in your ERC721 or the uri function in your ERC1155 contract should return an HTTP or IPFS URL, such as https://metadata.nftify.network/ipfs/43386991863816464903773437711726767830435150118599033599737883779213817849333. When queried, this URL should in turn return a JSON blob of data with the metadata for your token.

2. Using Ownable

For developers to set up contracts on NFTify automatically.

Read more about OpenZeppelin contracts here.

3. Metadata Structure

NFTify supports metadata that is structured according to the official ERC721 metadata standard.

Furthermore, we support various other properties that allow for multimedia attachments - including audio, video, and 3D models - as well as interactive traits for your items, giving you all the sorting and filtering capabilities on the NFTify marketplace.

Here's an example of metadata for a NFT on NFTify.

{
  "name":"GRSE-R-3-2021",
  "description":"Rare Card",
  "image":"https://data.nftify.network/ipfs/QmXYTfp61bxYcSEFGWm7qEr6qMYdkx7YocBG85th6mQPA9",
  "external_url":"https://wolflexnft.nftify.network/nft/grser32021",
  "attributes":[],
  "artist":"0x45d1A075c51186291a2eB914cbC7B0efe17BDDe8"
}

Here is how each of these properties work:

4. Attributes

We also allow you to add custom "attributes" to your metadata that will appear beneath each of your assets to give your items a little more pizazz.

To generate those attributes, the following array of attributes was included in the metadata:

... 
{ 
"attributes": [ 
    { 
      "trait_type": "Base", 
      "value": "Hamster" 
    }, 
    { 
      "trait_type": "Eyes", 
      "value": "Small" 
    }, 
    { 
      "trait_type": "Size", 
      "value": "Small" 
    }, 
    { 
      "trait_type": "Stamina", 
      "value": 3 
    }, 
    { 
      "display_type": "boost_number", 
      "trait_type": "Power", 
      "value": 3 
    }, 
    { 
      "display_type": "boost_percentage", 
      "trait_type": "Stamina", 
      "value": 10 
    }, 
    { 
      "display_type": "number", 
      "trait_type": "Generation", 
      "value": 3 
    } 
  ] 
}

Here trait_type is the name of the trait, value is the value of the trait, and display_type is a field indicating how you would like it to be displayed. For string traits, you don't have to worry about display_type.

4.1. Numeric Traits

For numeric traits, NFTify currently supports three options: number, boost_percentage, and boost_number (similar to boost_percentage but doesn't show a percent sign). If you pass in a value that's a number and you don't set a display_type, the trait will appear in the Levels section.

Adding an optional max_value sets a ceiling for a numerical trait's possible values. It defaults to the maximum that NFTify has seen so far on the assets on your contract. If you set a max_value, make sure not to pass in a higher value.

4.2. Date Traits

NFTify also supports a date display_type. Traits of this type will appear below "Boosts." Pass in a unix timestamp as the value.

 { 
   "display_type": "date", 
   "trait_type": "birthday", 
   "value": 1637033050 
 }

If you don't want to have a trait_type for a particular trait, you can include just a value in the trait and it will be set as a generic property. For example,

{ 
  "value": "Happy" 
}

5. Attribute guidelines

When coming up with your attributes, you should include string attributes as strings (remember the quotes), and numeric properties as either floats or integers so that NFTify can display them properly. String properties should be human-readable strings.

6. IPFS

NFTify supports the storage of NFT metadata in decentralized file networks like IPFS, so that they can’t be modified by a central party.

If you use IPFS to host your metadata, your URL should be in the format ipfs://<hash>. For example, ipfs://QmTy8w65yBXgyfG2ZBg5TrfB2hPjrDQH3RCQFJGkARStJb. If you plan to store on IPFS, we recommend Pinata for easily storing data. Here's a tutorial by Chainlink for getting started: https://blog.chain.link/build-deploy-and-sell-your-own-dynamic-nft/.