Below is an example of the JSON blob which is returned from the smart contract function tokenUri(uint256 tokenId) this is often termed token metadata by people working with Web3 products. There are other types of metadata that KnownOrigin stores on-chain such as creator, edition size as well as other derived metadata such as token sale state and sale type, this extra onchain metadata is not covered by this article, and this guide only refers to JSON based, tokenURI metadata.
In general, we loosely follow OpenSea's standard along with including extra fields as we need.
Not all tokens have every property, this is due to either the age of the token i.e., metadata fields has evolved over time but also not all fields are required i.e., image assets don't need a cover image or animation_url.
Any example of a fully populated metadata can be found below.
{ "name": "Test", "description": "Test", "attributes": { "artist": "KnownOrigin", "scarcity": "rare", "format": "the-format", "theme": "the-theme", "production_year": 2021, "tags": [ "abstract", "acrylics", "another-tag" ], "asset_type": "video/mp4", "asset_size_in_bytes": 38247618, "cover_image_type": "image/png", "cover_image_size_in_bytes": 7588405 }, "image_sphere": true, "cover_image_set": true, "external_uri": "https://knownorigin.io/artists/0x3f8c962eb167ad2f80c72b5f933511ccdf0719d4", "image": "ipfs://ipfs/QmbayRoC4vECrNiJ3yAFK3YQ9MzAfhKgpAspNLRSBc8ZeV/asset.png", "animation_url": "ipfs://ipfs/QmSoBGYCdZi1zMkZJytiYbyCG3dPKaG4fJmyQzAKihKfW3/asset.mp4", "artist": "0x3f8c962eb167ad2f80c72b5f933511ccdf0719d4" }image- the image OR cover image used for displaying the visual aspect of any KnownOrigin assetsanimation_url- the video, 3D or other interactive/animation assets to display
How is it stored?
We currently use IPFS, InterPlanetary File System, for storing metadata and images. The InterPlanetary File System is a protocol and peer-to-peer network for storing and sharing data in a distributed file system.
The IPFS network enabled files to be uploaded and stored by a network of willing participants, in a network of peer-to-peer nodes. It also has other additional, important, features such as content addressable data, also known as IPFS hashes or CIDs (Content Identifiers). This means that the data uploaded produces a unique fingerprint based on the data itself, enabling you to prove the data stored on IPFS marries up to the reference kept on-chain, along with ensuring it cannot be changed for something else as the hash would also change.
We currently pin the data to Infura and Pinata to provide a more robust level of pinning security.
You will also often see it referenced as ipfs://ipfs/{HASH} or ipfs://{HASH} - copy the hash to resolve this pinned data and then use any ipfs gateway to find the actual content.