Preparing the NFT files

Prepare visual assets and ERC-721/ERC-1155 metadata JSON files for NFT minting on Chiliz Chain, covering image formats and metadata schema standards.

Preparing the files for your NFT project involves two distinct parts:

• the visual asset (what the user sees)

• the metadata (what the blockchain reads)

The visual assets

This is the art that you want to turn into NFTs.

You (or your design team) should produce the files with these specifications:

Format

• Static images: Use PNG (preferred for quality) or JPG.

• Video: Use MP4. _If you have a video card, also create a static "thumbnail" image for smooth loading._

• 3D Objects: Use GLB or GLTF.

Dimensions (Aspect Ratio)

Usually, NFTs use either:

• A square format: 1080 x 1080 pixels.

• A Vertical Phone/Story format: 1080 x 1920 pixels.

File Size

Aim to keep the files under 25MB (ideally <10MB) for fast loading on mobile wallets.

Pro Tip

Create a high-res "Master" file (100MB+) but do not use it as the main NFT image. Instead, use the "Unlockable Content" feature to give the Master file only to the owner.

The metadata

The blockchain does not store your image directly (it is too expensive). It stores a link to a text file in the JSON format, which means the JSON files can only be created once the visual files are effectively hosted.

Most modern tooling will do this for you, saving you from having to do it all by hand.

There must be one JSON file for each NFT type in your collection (e.g., one JSON for "NFT 1", one for "NFT 2", etc.).

Here is an example of an NFT's JSON file:

{
  "name": "Mark Whaleon - 2024/25 Season",
  "description": "The official Striker card for Team X, 2024/25 Season. Gold Tier.",
  "image": "ipfs://YOUR_IMAGE_IPFS_ID_GOES_HERE",
  "external_url": "https://example.com/players/whaleon",
  "attributes": [
    {
      "trait_type": "Position",
      "value": "Striker"
    },
    {
      "trait_type": "Jersey Number",
      "value": "10"
    },
    {
      "trait_type": "Season",
      "value": "2024/2025"
    },
    {
      "trait_type": "Rarity",
      "value": "Gold"
    },
    {
      "display_type": "number",
      "trait_type": "Goals Scored",
      "value": 15
    }
  ]
}

The attributes are crucial for sports-related cards. It allows fans to filter by "Position," "Season," or "Rarity" on marketplaces.