Access Controls

Control who can buy your NFTs

Access Lists

Accesslist support is a premium feature. To get started, contact sales

Crossmint allows you to whitelist both wallet and email addresses. Once the team has approved your request, you will need to provide the following information:

1. Your Crossmint clientId or collectionId for the collection.

2. The list of wallet and email addresses to be included in the accesslist.

If you whitelist users’ email addresses, Crossmint will create wallets associated with those email addresses and provide them to you for inclusion in the accesslist. Users will then be able to authenticate during the purchase and execute the transaction.

EVM

You can set up accesslists using Merkle Trees or inserting the list of whitelisted addresses directly on the smart contract:

A. Merkle Tree Accesslists

While using Merkle Trees is more gas-efficient, it involves a slightly more complex setup. Here is an example accesslist mint function:

See Example

Solidity

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract Accesslist is ERC721, Ownable {
    bytes32 public merkleRoot;
    uint256 public nextTokenId;
    mapping(address => bool) public claimed;

    constructor() ERC721("ExampleNFT", "NFT") {
        merkleRoot = 0x0;
    }

    function isWhiteListed(bytes32[] memory proof, bytes32 leaf) public view returns(bool) {
        return MerkleProof.verify(proof, merkleRoot, leaf);
    }

    function setMerkleRoot(bytes32 merkleRoot_) external onlyOwner {
        merkleRoot = merkleRoot_;
    }

    function mint(address to, bytes32[] calldata merkleProof) public payable {
        require(claimed[to] == false, "already claimed");
        claimed[to] = true;
        require(
            isWhiteListed(
                merkleProof,
                keccak256(abi.encodePacked(to))
            ),
            "invalid merkle proof"
        );
        nextTokenId++;
        _mint(to, nextTokenId);
    }
}

B. Mapping-Based Accesslists

The most straightforward method of whitelisting involves maintaining a mapping of the whitelisted addresses within your smart contract. This approach is faster but consumes more gas and savvy developers may be able to determine the addresses of the accesslist.

See Example

Solidity

mapping(address => uint256) public whitelistMapping;

Solidity

function presale(address _to, uint256 _count) external payable {
    // ensure _to address has tokens left to mint
    require(whitelistMapping[_to] > 0, "no whitelist tokens for user");

    // decrement mapping for user
    whitelistMapping[_to] -= _count;

    // presale minting logic here
}

You can set up accesslists using Merkle Trees or inserting the list of whitelisted addresses directly on the smart contract:

A. Merkle Tree Accesslists

While using Merkle Trees is more gas-efficient, it involves a slightly more complex setup. Here is an example accesslist mint function:

See Example

Solidity

//SPDX-License-Identifier: Unlicense
pragma solidity ^0.8.0;

import "@openzeppelin/contracts/utils/cryptography/MerkleProof.sol";
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/access/Ownable.sol";

contract Accesslist is ERC721, Ownable {
    bytes32 public merkleRoot;
    uint256 public nextTokenId;
    mapping(address => bool) public claimed;

    constructor() ERC721("ExampleNFT", "NFT") {
        merkleRoot = 0x0;
    }

    function isWhiteListed(bytes32[] memory proof, bytes32 leaf) public view returns(bool) {
        return MerkleProof.verify(proof, merkleRoot, leaf);
    }

    function setMerkleRoot(bytes32 merkleRoot_) external onlyOwner {
        merkleRoot = merkleRoot_;
    }

    function mint(address to, bytes32[] calldata merkleProof) public payable {
        require(claimed[to] == false, "already claimed");
        claimed[to] = true;
        require(
            isWhiteListed(
                merkleProof,
                keccak256(abi.encodePacked(to))
            ),
            "invalid merkle proof"
        );
        nextTokenId++;
        _mint(to, nextTokenId);
    }
}

B. Mapping-Based Accesslists

The most straightforward method of whitelisting involves maintaining a mapping of the whitelisted addresses within your smart contract. This approach is faster but consumes more gas and savvy developers may be able to determine the addresses of the accesslist.

See Example

Solidity

mapping(address => uint256) public whitelistMapping;

Solidity

function presale(address _to, uint256 _count) external payable {
    // ensure _to address has tokens left to mint
    require(whitelistMapping[_to] > 0, "no whitelist tokens for user");

    // decrement mapping for user
    whitelistMapping[_to] -= _count;

    // presale minting logic here
}

You can set up accesslists on your Candy Machine using Merkle Trees or SPL Tokens

A. Merkle Tree Accesslists

Simply send the user IDs to Crossmint. Once you have the Merkle proof, you can pass it into the Crossmint Hosted Checkout lineItems.callData as a string, as in the example below:

See Example

React

<CrossmintProvider apiKey="_YOUR_CLIENT_API_KEY_">
    <CrossmintHostedCheckout
        lineItems={{
            collectionId: "crossmint:_YOUR_COLLECTION_ID_",
            callData: {
                type: "candy-machine",
                quantity: 1,
                mintingGroup: "pre",
                merkleProof: "62, 43, 204, 46, 222, 219, 236, 32, 60, 4, 235, [...]",
            }
        }}
    />
</CrossmintProvider>

B. SPL Token-based Accesslists

You can whitelist wallets by airdropping them SPL tokens.

Geofencing

Geofencing support is a premium feature only available to customers on a paid plan. To get started, contact sales

Crossmint supports geofencing capabilities through our Customer Success Engineering (CSE) team. Our CSE team can work with you to block transactions from specific countries or geographic regions via Stripe rules.

To set up geofencing for your project, please contact our sales team to discuss your specific requirements and implementation details.