Configure Metadata for Collections and Tokens

Collection and token metadata play a crucial role in contextualizing and enhancing digital assets by providing additional properties, such as a name, description, and image. Configuring collection and token metadata at the contract level allows Reservoir to more efficiently and accurately index and return this data in our APIs and other services.

Contract URI

For contract or collection level metadata, you can add a contractURI method to your ERC721 or ERC1155 contract. Below is a sample.

contract myFirstContract is ERC721 {
    function contractURI() public view returns (string memory) {
        return "ipfs://UyNGgv3jx2HHfBjQX9RnKtxj2xv2xQDtbVXoRi5rJ31234";
        // or e.g. https://myDomain.com/myFirstContractMetadata.json
    }
}

Your IPFS or URL should return a JSON blob that is formatted like the example before. These are all possible properties but only name is required.

{
  "name": ["name"], //required
  "description": ["description"],
  "imageUrl": ["image", "image_url"],
  "bannerImageUrl": ["cover_image", "banner_image_url"],
  "externalUrl": ["website", "website_url", "external_url"],
  "twitterUrl": ["twitter"],
  "twitterUsername": ["twitter_username"],
  "discordUrl": ["discord", "discord_url"],
  "instagramUrl": ["instagram"],
  "telegramUrl": ["telegram"],
  "githubUrl": ["github"],
  "mediumUrl": ["medium"],
}
PropertyDescription
nameContract's Name (required)
descriptionReadable description for end users. Markdown supported.
imageUrlURL to the contract's image. We support any image format (SVG, PNG, etc.) and can be IPFS URLS or paths. Recommended size is 350x350.
bannerImageUrlURL to the contract's banner image for the contract page. We support any image format (SVG, PNG, etc.) and can be IPFS URLS or paths.
externalUrlURL to view contract on an external page or the website for the contract.
twitterUrlURL to the contract's Twitter page.
twitterUsernameTwitter username to link out to, @ is not necessary before the name.
discordUrlURL to the contract's Discord server.
instagramUrlURL to the contract's Instagram account.
telegramUrlURL to the contract's Telegram account or announcement channel.
githubUrlURL to the contract's GitHub page.
mediumUrlURL to the contract's Medium page.

Token URI

Your contract needs to return a URI so Reservoir can pull off-chain metadata for ERC721 and ERC1155 assets. We use the tokenURI method on ERC721 and the uri method in ERC1155 to find your URI.

Here is a sample of how the tokenURI method should look 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)
  );
}

Either the ERC721'stokenURI or the ERC1155'suri should return an HTTP or IPFS URL. The URL should return a JSON blob of data with your token's metadata. Reservoir supports the official ERC721 metadata standard or the Enjin metadata suggestions. We also support other multimedia properties to allow the options of audio, video, 3D models, and interactive traits.

Here is a sample JSON response when the URL is polled.

{
  "name": "NFT #100001",
  "description": "This is an NFT collection launched on Ethereum", 
  "image": "ipfs://QmYCduapLWPhnvw8AG7rBpn6eBbLRYeNqdt7FexjAQ123H", 
  "attributes": [ ... ]
  "external_url": "http://www.ethereumNFTcollection.com/", 
}

Below details the possible token metadata properties. The maximum file size for media is 100MB but we recommend keeping it under 100MB for efficient load times.

PropertyDescription
nameItem's Name
descriptionReadable description for end users. Markdown supported.
imageURL to the item's image. We support any image format (SVG, PNG, etc.) and can be IPFS URLS or paths. Recommended size is 350x350.
attributesThese are the attributes of an item. References below for fomatting.
background_colorItem's background color when displayed on Reservoir. Must use a six-character hexadecimal without a pre-pended #.
external_urlURL to view the item on an external site.
animation_urlURL to a multi-media attachment. These file extensions are supported: GLTF, GLB, WEBM, MP4, M4V, OGV, OGG, MP3, WAV, and OGA
youtube_urlURL to YouTube video.

Token Attributes

Attributes are optional for your Token URI but allow you to distinguish your NFTs from one another in the contract. Rarity scores can be created based on attributes; read more about rarity scores here.

Below is a sample for how to format your attributes.

...
{
"attributes": [
    {
      "trait_type": "Background", 
      "value": "Silver"
    }, 
    {
      "trait_type": "Hat", 
      "value": "Green"
    }, 
    {
      "trait_type": "Cheeks", 
      "value": "Rosey"
    }, 
    {
      "trait_type": "Stage", 
      "value": 3
    }, 
    {
      "trait_type": "Energy", 
      "value": 6
    }, 
    {
      "trait_type": "Mood", 
      "value": "Angry"
    }, 
    {
      "display_type": "multiplier_number", 
      "trait_type": "Defense", 
      "value": 2
    }, 
    {
      "display_type": "multiplier_percentage", 
      "trait_type": "Attack", 
      "value": 40
    }, 
    {
      "display_type": "number", 
      "trait_type": "Lives", 
      "max_value": 3,
      "value": 3
    },
    {
      "display_type": "date", 
      "trait_type": "birthday", 
      "value": 1636922382
    }
  ]
}
TypeDescription
trait_typeName of the trait; case sensitive
valueValue of the trait; case sensitive
display_typeIndicates how to display it; optional for numbers; skip for string values
multiplier_numberInteger or float number value; not displayed as a percentage; multiplier can be renamed
multiplier_percentageInteger or float number value displayed with a percentage sign; multiplier can be renamed
numbersInteger or float number value; not displayed as a percentage
max_valueSet a maximum limit for a numerical trait; optional; value cannot exceed max_value if defined
dateSupports unix timestamp (seconds) value

Metadata Updates

ERC4906, an extension of ERC721, introduces MetadataUpdate events to simplify the update of metadata associated with ERC721 tokens. As explained in the official ERC-4906 proposal, emitting an on-chain event allows Reservoir and other providers to know when to refresh the metadata. This is strongly recommended especially in cases with dynamic NFTs.

To refresh a token, you can emit an event like the sample below.

event MetadataUpdate(uint256 _tokenId);
event BatchMetadataUpdate(uint256 _fromTokenId, uint256 _toTokenId);

To refresh a entire contract, emit _toTokenId with type(uint256).max.

For ERC1155, metadata updated can be triggered with the specification for the event URI:

event URI(string _value, uint256 indexed _id);

On-chain metadata updates are recommended whenever possible, however, Reservoir also supports refreshing collections and tokens via our APIs.

Note: These refresh APIs should be used in moderation. Calling it in bulk or programmatically will result in your API key getting rate limited.