Bring Your Own Contract

Crossmint has a pre-audited library of smart contracts that serve most use cases. However, if you have custom needs, you can also bring your own contract and leverage Crossmint’s scalable infrastructure to mint and distribute the NFTs. Crossmint will execute transactions at the maximum rate the blockchain can handle, pay gas fees, and create wallets for users who don’t have one, all with enterprise SLAs and customer support.

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Prerequisites

• Your minting contract must have a function that allows free mints. This function must whitelist one of Crossmint’s treasury addresses. Contact us to obtain the wallet address to whitelist.
• NFTs must follow the ERC721 standard. For ERC1155 support, contact us.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.9;

import "@openzeppelin/contracts/access/AccessControl.sol";

...

contract BYOCMinter is ERC721, AccessControl {

    bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");

    constructor() payable ERC721("EVM 721 Starter", "XMPL") {
        _grantRole(MINTER_ROLE, msg.sender);

        // THIS IS THE IMPORTANT DETAIL. YOUR CROSSMINT ENGINEER WILL PROVIDE THE WALLET ADDRESS
        _grantRole(MINTER_ROLE, <ENTER_WALLET_PROVIDED_BY_CROSSMINT_TEAM>);
    }

    function mint(address _to, string calldata uri) external onlyRole(MINTER_ROLE) {
        // mint function logic
    }
}

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Integration Guide

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1. Register Your Smart Contract

On the console, go to the "Collections" tab and click on New collection. Next, follow the steps in the wizard to enter your contract details and identify the function used to mint NFTs. Refer to the section below for common advanced scenarios when importing your contract.

// Example generated abi file for smart contract
{
    "abi": [
        {
            "inputs": [],
            "stateMutability": "nonpayable",
            "type": "constructor"
        },
        {
            "inputs": [
                {
                    "internalType": "address",
                    "name": "_to",
                    "type": "address"
                }
            ],
            "name": "mintTo",
            "outputs": [],
            "stateMutability": "payable",
            "type": "function"
        }
    ]
}

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2. Contract Review

Copy the collectionID from the collection page in the Crossmint console and share it with your Crossmint point of contact. The team will validate the contract meets the requirements, set it up to be used with the minting tools, and provide you a new collectionID which you can use to make calls to the API.

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3. Mint

You can now invoke any of the “minting” functions documented in the API reference. Contact us if you need access to any other function, like editing or burning.

The body of the request should follow this structure:

{
    "recipient": "<chain>:<address>", // or <email:<email_address>:<chain>
    "contractArguments": {
        // JSON object with the arguments to the mint function and specified value
    }
}

For example:

{
  "recipient": "polygon:0xasimo..."
  "contractArguments": {
    "quantity": 1,
    "signature": "0xabc..."
  }
}

This request will mint and deliver the NFT. If you specify an email address as the recipient, it will create a wallet on-the-fly.

Refer back to the minting guide to learn how to listen to mint completion, and minting API reference for advanced options.