Nft Marketplace

When to activate

• Creating NFT collections (PFP, art, gaming, utility)
• Building NFT marketplace or auction contracts
• Implementing ERC-2981 royalty standards
• Designing dynamic NFTs with on-chain metadata
• Integrating with OpenSea, Blur, or custom marketplaces

When NOT to use

• For fungible token (ERC-20) development
• For centralized digital asset management
• For physical art inventory systems

Instructions

1. Choose standard. ERC-721 (unique), ERC-1155 (semi-fungible/batch), ERC-6551 (token-bound accounts).
2. Design metadata. On-chain vs off-chain (IPFS/Arweave). Follow OpenSea metadata schema. Include traits, rarity.
3. Implement minting. Allowlist (Merkle tree), public sale, Dutch auction, or reveal mechanics.
4. Add royalties. ERC-2981 for on-chain royalty info. Operator filter for marketplace enforcement.
5. Build marketplace. Listings, offers, auctions (English/Dutch). Escrow pattern for safe transfers.
6. Gas optimization. Batch minting (ERC-1155), lazy minting (sign-to-mint), compressed metadata.
7. Security. Prevent double-spend, reentrancy in transfers, enumeration attacks on large collections.

Example

// ERC-721 with Merkle allowlist mint
contract NFTCollection is ERC721, ERC721Enumerable {
    bytes32 public merkleRoot;
    mapping(address => bool) public claimed;
    
    function allowlistMint(bytes32[] calldata proof) external {
        require(!claimed[msg.sender], "Already claimed");
        require(MerkleProof.verify(proof, merkleRoot, keccak256(abi.encodePacked(msg.sender))));
        claimed[msg.sender] = true;
        _safeMint(msg.sender, totalSupply() + 1);
    }
}