Metadata

Understand NFT metadata standards

Crossmint’s minting infrastructure can validate and upload metadata to decentralized storage on your behalf. Crossmint will default to IPFS. If you are interested in using Arweave, contact us. If you want to upload and manage the metadata yourself, simply pass the url to the API and flag reuploadLinkedFiles as false.

Collection and NFT metadata (e.g. title, description, image) must be specified in JSON format and follow industry conventions to ensure it renders appropriately across wallets and marketplaces.

Crossmint supports rich metadata like audio, video, and HTML. To include rich metadata, simply populate animation_url as specified in the links below.

File size limits

Crossmint’s standard plan has a 10mb file size limit. For larger uploads, you must upgrade to a premium plan or handle the upload yourself.

Metadata standards differ slightly across blockchains:

• EVM chains
• Solana
• Aptos

EVM chains follow the OpenSea standard. Refer to their official documentation to see what attributes can be included and how. Note that name and image are mandatory fields.

EVM Metadata Example

{
  "name": "Crossmint Test NFT",
  "description": "Created with the Crossmint minting API",
  "image": "https://bafkreiexjl6kw4khdxkrt6dojgacscnzvrys47t472l2t7d6r2ss65kifq.ipfs.nftstorage.link/",
  "external_url": "https://docs.crossmint.com",
  "attributes":  [
    {
      "trait_type": "background",
      "value": "black"
    },
    {
      "trait_type": "flavor",
      "value": "minty"
    }
  ]
}

---

FAQs

What type of files can I store?

You may store any text and image file. Additionally, you may include multi-media files such as GLTF, GLB, WEBM, MP4, M4V, OGV, and OGG, along with the audio-only extensions MP3, WAV, and OGA. Please stored them as animation_url.

In addition, animation_url also supports HTML pages, allowing you to build rich experiences and interactive NFTs using JavaScript canvas, WebGL, and more. Scripts and relative paths within the HTML page are also supported. However, access to browser extensions is not supported.

What's the maximum file size?

The maximum file size is 10mb. For larger files, you must upgrade to an enterprise plan or upload the metadata yourself and pass the URI to the API.

Can I store the metadata on a centralized server?

Yes. You must handle the upload yourself and pass the URL to the API.