Nft Standards

---
name: nft-standards
description: Implement NFT standards (ERC-721, ERC-1155) with proper metadata handling, minting strategies, and marketplace integration. Use when creating NFT contracts, building NFT marketplaces, or implementing digital asset systems.
---

# NFT Standards

Master ERC-721 and ERC-1155 NFT standards, metadata best practices, and advanced NFT features.

## When to Use This Skill

- Creating NFT collections (art, gaming, collectibles)
- Implementing marketplace functionality
- Building on-chain or off-chain metadata
- Creating soulbound tokens (non-transferable)
- Implementing royalties and revenue sharing
- Developing dynamic/evolving NFTs

## ERC-721 (Non-Fungible Token Standard)

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC721/extensions/ERC721URIStorage.sol";
import "@openzeppelin/contracts/token/ERC721/extensions/ERC721Enumerable.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
import "@openzeppelin/contracts/utils/Counters.sol";

contract MyNFT is ERC721URIStorage, ERC721Enumerable, Ownable {
    using Counters for Counters.Counter;
    Counters.Counter private _tokenIds;

    uint256 public constant MAX_SUPPLY = 10000;
    uint256 public constant MINT_PRICE = 0.08 ether;
    uint256 public constant MAX_PER_MINT = 20;

    constructor() ERC721("MyNFT", "MNFT") {}

    function mint(uint256 quantity) external payable {
        require(quantity > 0 && quantity <= MAX_PER_MINT, "Invalid quantity");
        require(_tokenIds.current() + quantity <= MAX_SUPPLY, "Exceeds max supply");
        require(msg.value >= MINT_PRICE * quantity, "Insufficient payment");

        for (uint256 i = 0; i < quantity; i++) {
            _tokenIds.increment();
            uint256 newTokenId = _tokenIds.current();
            _safeMint(msg.sender, newTokenId);
            _setTokenURI(newTokenId, generateTokenURI(newTokenId));
        }
    }

    function generateTokenURI(uint256 tokenId) internal pure returns (string memory) {
        // Return IPFS URI or on-chain metadata
        return string(abi.encodePacked("ipfs://QmHash/", Strings.toString(tokenId), ".json"));
    }

    // Required overrides
    function _beforeTokenTransfer(
        address from,
        address to,
        uint256 tokenId,
        uint256 batchSize
    ) internal override(ERC721, ERC721Enumerable) {
        super._beforeTokenTransfer(from, to, tokenId, batchSize);
    }

    function _burn(uint256 tokenId) internal override(ERC721, ERC721URIStorage) {
        super._burn(tokenId);
    }

    function tokenURI(uint256 tokenId) public view override(ERC721, ERC721URIStorage) returns (string memory) {
        return super.tokenURI(tokenId);
    }

    function supportsInterface(bytes4 interfaceId)
        public
        view
        override(ERC721, ERC721Enumerable)
        returns (bool)
    {
        return super.supportsInterface(interfaceId);
    }

    function withdraw() external onlyOwner {
        payable(owner()).transfer(address(this).balance);
    }
}
```

## ERC-1155 (Multi-Token Standard)

```solidity
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/token/ERC1155/ERC1155.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract GameItems is ERC1155, Ownable {
    uint256 public constant SWORD = 1;
    uint256 public constant SHIELD = 2;
    uint256 public constant POTION = 3;

    mapping(uint256 => uint256) public tokenSupply;
    mapping(uint256 => uint256) public maxSupply;

    constructor() ERC1155("ipfs://QmBaseHash/{id}.json") {
        maxSupply[SWORD] = 1000;
        maxSupply[SHIELD] = 500;
        maxSupply[POTION] = 10000;
    }

    function mint(
        address to,
        uint256 id,
        uint256 amount
    ) external onlyOwner {
        require(tokenSupply[id] + amount <= maxSupply[id], "Exceeds max supply");

        _mint(to, id, amount, "");
        tokenSupply[id] += amount;
    }

    function mintBatch(
        address to,
        uint256[] memory ids,
        uint256[] memory amounts
    ) external onlyOwner {
        for (uint256 i = 0; i < ids.length; i++) {
            require(tokenSupply[ids[i]] + amounts[i] <= maxSupply[ids[i]], "Exceeds max supply");
            tokenSupply[ids[i]] += amounts[i];
        }

        _mintBatch(to, ids, amounts, "");
    }

    function burn(
        address from,
        uint256 id,
        uint256 amount
    ) external {
        require(from == msg.sender || isApprovedForAll(from, msg.sender), "Not authorized");
        _burn(from, id, amount);
        tokenSupply[id] -= amount;
    }
}
```

## Metadata Standards

### Off-Chain Metadata (IPFS)

```json
{
  "name": "NFT #1",
  "description": "Description of the NFT",
  "image": "ipfs://QmImageHash",
  "attributes": [
    {
      "trait_type": "Background",
      "value": "Blue"
    },
    {
      "trait_type": "Rarity",
      "value": "Legendary"
    },
    {
      "trait_type": "Power",
      "value": 95,
      "display_type": "number",
      "max_value": 100
    }
  ]
}
```

### On-Chain Metadata

```solidity
contract OnChainNFT is ERC721 {
    struct Traits {
        uint8 background;
        uint8 body;
        uint8 head;
        uint8 rarity;
    }

    mapping(uint256 => Traits) public tokenTraits;

    function tokenURI(uint256 tokenId) public view override returns (string memory) {
        Traits memory traits = tokenTraits[tokenId];

        string memory json = Base64.encode(
            bytes(
                string(
                    abi.encodePacked(
                        '{"name": "NFT #', Strings.toString(tokenId), '",',
                        '"description": "On-chain NFT",',
                        '"image": "data:image/svg+xml;base64,', generateSVG(traits), '",',
                        '"attributes": [',
                        '{"trait_type": "Background", "value": "', Strings.toString(traits.background), '"},',
                        '{"trait_type": "Rarity", "value": "', getRarityName(traits.rarity), '"}',
                        ']}'
                    )
                )
            )
        );

        return string(abi.encodePacked("data:application/json;base64,", json));
    }

    function generateSVG(Traits memory traits) internal pure returns (string memory) {
        // Generate SVG based on traits
        return "...";
    }
}
```

## Royalties (EIP-2981)

```solidity
import "@openzeppelin/contracts/interfaces/IERC2981.sol";

contract NFTWithRoyalties is ERC721, IERC2981 {
    address public royaltyRecipient;
    uint96 public royaltyFee = 500; // 5%

    constructor() ERC721("Royalty NFT", "RNFT") {
        royaltyRecipient = msg.sender;
    }

    function royaltyInfo(uint256 tokenId, uint256 salePrice)
        external
        view
        override
        returns (address receiver, uint256 royaltyAmount)
    {
        return (royaltyRecipient, (salePrice * royaltyFee) / 10000);
    }

    function setRoyalty(address recipient, uint96 fee) external onlyOwner {
        require(fee <= 1000, "Royalty fee too high"); // Max 10%
        royaltyRecipient = recipient;
        royaltyFee = fee;
    }

    function supportsInterface(bytes4 interfaceId)
        public
        view
        override(ERC721, IERC165)
        returns (bool)
    {
        return interfaceId == type(IERC2981).interfaceId ||
               super.supportsInterface(interfaceId);
    }
}
```

## Additional patterns and templates

More detailed templates and worked examples live in `references/details.md`. Read that file for the full pattern library.

Run this skill on a real model without leaving the page. Every run is saved to your history for this skill.

How to use

1. 1Save the content below as SKILL.md in your agent's skills directory (e.g. .claude/skills/<name>/SKILL.md).
2. 2Or paste it directly into the conversation as context before asking the agent to do the task.
3. 3Adjust any project-specific paths or conventions mentioned in the skill to match your setup.