Marmalade NG Metadata

The URI of a token (as retrieved by get-uri) must point to a JSON off-chain Metadata Object.

It is highly recommended to only store metadata (and NFTs related content like images) in reliable, immutable and long term storage. As such URI starting with https:// or http:// must be avoided. And Marketplaces should tag these NFTs as unsafe.

The 2 available options for NFT storage are either:

In case of IPFS, the URI must not include an `https` gateway.: Only the raw CID prefixed by ipfs:// must be present.

Note that the reference implementation of Marmalade NG: (https://explorer.marmalade-ng.xyz) supports in native ipfs and kdafs.

Specification

A token metadata has the following format:

JSON Metadata

Field Name

Data Type

Description

name

string

Identifies the asset to which this NFT represents.

description

string

Describes the asset to which this NFT represents.

image

string
A URI pointing to a resource with mime type image/* representing the asset
to which this NFT represents. Consider making any images at a width between
320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive.
The string may be a an embedded image in dataURI format as per RFC 2397.
attributes
(Optional)

array of objects
An array of objects, each representing a characteristic or trait of the
NFT, with a trait_type field specifying the trait’s name and a value
field specifying the trait’s value.
properties
(Optional, see below)

object

Arbitrary properties. Values may be strings, numbers, object or arrays.
JSON Metadata (properties object)

Field Name

Data Type

Description
authors
(Optional)

array of objects
An array of authors who created or contributed to the asset. Each author
is an object with a name field specifying the author’s name.
external_url
(Optional)

string

URL to an external application or website where users can also view the asset.
animation_url
(Optional)

string
URL to a multimedia attachment of the asset. The supported file formats are
MP4 and MOV for video, MP3, FLAC and WAV for audio, GLB for AR/3D assets,
and HTML for HTML pages. You may use the ?ext={file_extension} query to
provide information on the file type.
collection
(Optional)

object
An object with a name field specifying the name of the collection, and a
family field specifying the larger category or group to which the collection belongs.

JSON Schema

{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://marmalade-ng/meta-schema-v1.json",
  "title": "Marmalade NG Metadata",
  "description": "Schema for Marmalade-NG polyfungible  metadata.",
  "type": "object",
  "required": [
    "name",
    "description",
    "image"
  ],
  "properties": {
    "name": {
      "type": "string",
      "description": "Identifies the asset to which this NFT represents."
    },
    "description": {
      "type": "string",
      "description": "Describes the asset to which this NFT represents."
    },
    "image": {
      "type": "string",
      "format": "uri",
      "description": "A URI pointing to a resource with mime type image/* representing the asset to which this NFT represents. Consider making any images at a width between 320 and 1080 pixels and aspect ratio between 1.91:1 and 4:5 inclusive."
    },
    "attributes": {
      "type": "array",
      "description": "An array of objects, each representing a characteristic or trait of the NFT",
      "items": {
        "type": "object",
        "required": [
          "trait_type",
          "value"
        ],
        "properties": {
          "trait_type": {
            "type": "string",
            "description": "Trait's name"
          },
          "value": {
            "description": "Traits'value"
          }
        }
      }
    },
    "properties": {
      "type": "object",
      "description": "Arbitrary properties. Values may be strings, numbers, object or arrays",
      "properties": {
        "external_url": {
          "type": "string",
          "format": "uri",
          "description": "URL to an external application or website where users can also view the asset."
        },
        "animation_url": {
          "type": "string",
          "format": "uri",
          "description": "URL to a multimedia attachment of the asset. The supported file formats are MP4 and MOV for video, MP3, FLAC and WAV for audio, GLB for AR/3D assets, and HTML for HTML pages. You may use the ?ext={file_extension} query to provide information on the file type."
        },
        "authors": {
          "type": "array",
          "items": {
            "type": "object",
            "description": "An array of authors who created or contributed to the asset.",
            "required": [
              "name"
            ],
            "properties": {
              "name": {
                "type": "string",
                "description": "The author's name."
              }
            }
          }
        },
        "collection": {
          "type": "object",
          "required": [
            "name",
            "family"
          ],
          "properties": {
            "name": {
              "type": "string",
              "description": "The name of the collection."
            },
            "family": {
              "type": "string",
              "description": "specifying the larger category or group to which the collection belongs"
            }
          }
        }
      }
    }
  }
}

Example

{
  "name": "Garfield",
  "description": "King of cats",
  "image": "https://en.wikipedia.org/wiki/Garfield_(character)#/media/File:Garfield_the_Cat.svg",
  "attributes": [
    {
      "trait_type": "height",
      "value": 3.5
    },
    {
      "trait_type": "weight",
      "value": 11.2
    },
    {
      "trait_type": "rank",
      "value": 1
    }
  ],
  "properties": {
    "external_url": "https://www.mozilla.org/fr/firefox/",
    "collection": {
      "name": "Royal cats",
      "family": "Cats"
    },
    "authors": [
      {
        "name": "Jim Davis"
      }
    ]
  }
}