Contract Presets
Immutable provides a set of preset contracts than can be used by customers to deploy known, battle-tested contracts to the zkEVM.
Immutable's preset contracts are equipped with features purpose-built for Web3 gaming, simplifying the integration process with Immutable's zkEVM platform.
These contracts can be deployed seamlessly via the Immutable Hub. For a comprehensive understanding of these contracts, please review the detailed documentation provided for each contract listed below.
We encourage you to delve into the capabilities offered by our ERC721 and ERC1155 preset contract, meticulously crafted to enhance the efficiency of game development on our platform.
Key smart contracts in the Immutable ecosystem are deployed at addresses listed here
Explore the smart contracts deployed on Immutable's zkEVM Mainnet via the Explorer
The Immutable zkEVM contracts package, @imtbl/zkevm-contracts, was recently deprecated. Please use the new Immutable Smart Contracts monorepo @imtbl/contracts where the zkEVM contracts have been moved to.
List of zkEVM Immutable Preset Contracts
| Contract | Type | Purpose | Useful For |
|---|---|---|---|
| ERC20 | Game Token Contract | Creating fungible tokens for your game. These tokens are typically traded on traditional centralized crypto exchanges, with all assets in an ERC20 contract being identical. |
|
| ERC721-Recommended | Game Asset Collection | Immutable's recommended smart contract for creating non-fungible assets (NFTs) for your game. Each asset has a unique token_id, and a single collection can contain different types of assets. This contract offers multiple batch minting functions for various gaming use cases. Implements the Operator Allowlist |
|
| ERC721-Mint By ID | Game Asset Collection | A limited ERC721 collection with fewer batch minting functions. While less versatile than the recommended preset, it's useful when all mints will use the less gas-efficient minting function where the minter specifies the token_id pre-mint. Implements the Operator Allowlist |
|
| ERC721-Base | Game Asset Collection | The base ERC721 contract that all Immutable ERC721 presets inherit from. This documentation should be used as a reference, but the collection should not be deployed without adding additional features from either Immutable or your game. | Base contract reference, not for standalone deployment. |
| ERC1155 | Game Asset Collection | Immutable's recommended smart contract for creating semi-fungible assets (SFTs) for your game. Most in-game assets are semi-fungible, making this the most practical gaming asset contract. A single collection can contain different types of assets, with each token_id delineating a different asset. Implements the Operator Allowlist |
|
| Multicaller2 | Utility Contract | A utility contract that batches multiple events into a single transaction. |
|
| Fee Splitter | Utility Contract | A utility contract that collects ERC20 tokens sent to it. When prompted, it will release a specific ERC20 token, or all ERC20 tokens, to a predetermined list of recipients in a pre-determined ratio. |
|
| Permits | Contract Feature | A feature in Immutable's presets that can be used instead of approvals. Permits do not require gas until the permitted action is executed, unlike approvals that incur gas fees immediately when granted. |
|
zkEVM Collection Requirements: Operator Allowlist
All in-game asset collections (i.e. ERC721 and ERC1155) deployed on Immutable's zkEVM must utilise the operator allowlist to protect content creator (eg: you, the game studio's) royalty fees and Immutable's 2% protocol fees.
This can be achieved through embedding the following into your smart contract collection designs:
Recommended Approach
For seamless implementation use or inherit Immutable's preset contracts tailored for gas-efficient creation of Web3 gaming assets on the zkEVM network. Immutable offers the following 3 preset contracts; these contracts implement the Operator Allowlist:
- Recommended Presets for Web3 Games:
- ImmutableERC721.sol - Multiple batch minting functions for optimised gas efficiency. Compatible with Minting API. Multiple batch minting functions for offering gas efficiencies for different Web3 gaming use cases.
- ImmutableERC1155.sol. Semi-fungible tokens. Compatible with Minting API.
- Alternative Presets:
- ImmutableERC721MintByID.sol. Single batch minting function requiring game studio to specify token_id at time of mint. Optimised for gas, yet less gas efficient than ImmutableERC721.sol. Compatible with Minting API.
Minimally Required Standard
If the above options are not compatible with your game design, it is mandatory for your collection to inherit the OperatorAllowlistEnforced.sol contract and adding necessary overrides to approve and transfer functions, allowing your collection to interact with the OperatorAllowlist. OperatorAllowlistEnforced includes the modifier functions to identify compliant smart contracts for approvals and transfers, ensuring the preservation of content creators’ royalty fees and protocol fees in third-party marketplace transactions.
We recommend using our presets, if you don’t then you need to implement our Operator Allowlist.
To make sure that creators receive their hard earned loyalties, Immutable requires that all collections of ERC-721/1155s deployed on Immutable zkEVM implement the Operator Allowlist. Not implementing will have these effects for your collection (i.e. ERC-721/1155s):
- You may forfeit any token grants you may have received.
- Passport users will receive a warnings that your collection is likely to be counterfeit.
- Your collection will not appear on any of the 3rd party marketplaces in our ecosystem.
For more information on the Operator Allowlist, please see this guide.
Example contracts using OpenZeppelin's ERC721 and ERC1155 standards with the OperatorAllowlistEnforced contract are provided below:
- ERC721
- ERC721 Upgradable
- ERC1155
- ERC1155 Upgradable
Below is an example ClashOfCatsERC721 contract that inherits our OperatorAllowlistEnforced:
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.19;
import '@openzeppelin/contracts/token/ERC721/ERC721.sol';
import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {OperatorAllowlistEnforced} from '@imtbl/contracts/contracts/allowlist/OperatorAllowlistEnforced.sol';
contract ClashOfCatsERC721 is ERC721, Ownable, OperatorAllowlistEnforced {
constructor(
string memory name,
string memory symbol,
address operatorAllowlist_
) ERC721(name, symbol) Ownable() {
// OAL address is set in the constructor
_setOperatorAllowlistRegistry(operatorAllowlist_);
}
// Overrides _approve function to include `validateApproval` modifier for OAL
function _approve(
address to,
uint256 tokenId
) internal override(ERC721) validateApproval(to) {
super._approve(to, tokenId);
}
// Overrides setApprovalForAll function to include `validateApproval` modifier for OAL
function setApprovalForAll(
address operator,
bool approved
) public override(ERC721) validateApproval(operator) {
super.setApprovalForAll(operator, approved);
}
// Overrides _transfer function to include `validateTransfer` modifier for OAL
function _transfer(
address from,
address to,
uint256 tokenId
) internal override(ERC721) validateTransfer(from, to) {
super._transfer(from, to, tokenId);
}
}
Below is an example ClashOfCatsERC721Upgradable contract that inherits our OperatorAllowlistEnforced:
pragma solidity 0.8.19;
import '@openzeppelin/contracts-upgradeable/token/ERC721/ERC721Upgradeable.sol';
import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {OperatorAllowlistEnforced} from '@imtbl/contracts/contracts/allowlist/OperatorAllowlistEnforced.sol';
contract ClashOfCatsERC721Upgradable is
ERC721Upgradeable,
OperatorAllowlistEnforced
{
function initialize(
string memory name_,
string memory symbol_,
address operatorAllowlist_
) public initializer {
__ERC721_init(name_, symbol_);
// OAL address is set in the constructor
_setOperatorAllowlistRegistry(operatorAllowlist_);
}
// Overrides approve function to include `validateApproval` modifier for OAL
function approve(
address to,
uint256 tokenId
) public virtual override(ERC721Upgradeable) validateApproval(to) {
super.approve(to, tokenId);
}
// Overrides setApprovalForAll function to include `validateApproval` modifier for OAL
function setApprovalForAll(
address operator,
bool approved
) public virtual override(ERC721Upgradeable) validateApproval(operator) {
super.setApprovalForAll(operator, approved);
}
// Overrides _safeTransfer function to include `validateTransfer` modifier for OAL
function _safeTransfer(
address from,
address to,
uint256 tokenId,
bytes memory _data
) internal virtual override(ERC721Upgradeable) validateTransfer(from, to) {
super._safeTransfer(from, to, tokenId, _data);
}
// Overrides transferFrom function to include `validateTransfer` modifier for OAL
function transferFrom(
address from,
address to,
uint256 tokenId
) public virtual override(ERC721Upgradeable) validateTransfer(from, to) {
super.transferFrom(from, to, tokenId);
}
}
Below is an example ClashOfCatsERC1155 contract that inherits our OperatorAllowlistEnforced:
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.19;
import '@openzeppelin/contracts/token/ERC1155/ERC1155.sol';
import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {OperatorAllowlistEnforced} from '@imtbl/contracts/contracts/allowlist/OperatorAllowlistEnforced.sol';
contract ClashOfCatsERC1155 is ERC1155, Ownable, OperatorAllowlistEnforced {
constructor(
string memory baseTokenURI,
address operatorAllowlist_
) ERC1155(baseTokenURI) Ownable() {
// OAL address is set in the constructor
_setOperatorAllowlistRegistry(operatorAllowlist_);
}
// Overrides _safeTransferFrom function to include `validateTransfer` modifier for OAL
function _safeTransferFrom(
address from,
address to,
uint256 id,
uint256 value,
bytes memory data
) internal override validateTransfer(from, to) {
super._safeTransferFrom(from, to, id, value, data);
}
// Overrides _safeBatchTransferFrom function to include `validateTransfer` modifier for OAL
function _safeBatchTransferFrom(
address from,
address to,
uint256[] memory ids,
uint256[] memory values,
bytes memory data
) internal override validateTransfer(from, to) {
super._safeBatchTransferFrom(from, to, ids, values, data);
}
// Overrides setApprovalForAll function to include `validateApproval` modifier for OAL
function setApprovalForAll(
address operator,
bool approved
) public override(ERC1155) validateApproval(operator) {
super.setApprovalForAll(operator, approved);
}
}
Below is an example ClashOfCatsERC1155Upgradable contract that inherits our OperatorAllowlistEnforced:
// SPDX-License-Identifier: UNLICENSED
pragma solidity 0.8.19;
import '@openzeppelin/contracts-upgradeable/token/ERC1155/ERC1155Upgradeable.sol';
import {Ownable} from '@openzeppelin/contracts/access/Ownable.sol';
import {OperatorAllowlistEnforced} from './OperatorAllowlistEnforced.sol';
contract ClashOfCatsERC1155Upgradable is
ERC1155Upgradeable,
OperatorAllowlistEnforced
{
function initialize(
string memory uri_,
address operatorAllowlist_
) public initializer {
__ERC1155_init(uri_);
// OAL address is set in the constructor
_setOperatorAllowlistRegistry(operatorAllowlist_);
}
// Overrides _safeTransferFrom function to include `validateTransfer` modifier for OAL
function _safeTransferFrom(
address from,
address to,
uint256 id,
uint256 value,
bytes memory data
) internal override(ERC1155Upgradeable) validateTransfer(from, to) {
super._safeTransferFrom(from, to, id, value, data);
}
// Overrides _safeBatchTransferFrom function to include `validateTransfer` modifier for OAL
function _safeBatchTransferFrom(
address from,
address to,
uint256[] memory ids,
uint256[] memory values,
bytes memory data
) internal override(ERC1155Upgradeable) validateTransfer(from, to) {
super._safeBatchTransferFrom(from, to, ids, values, data);
}
// Overrides setApprovalForAll function to include `validateApproval` modifier for OAL
function setApprovalForAll(
address operator,
bool approved
) public override(ERC1155Upgradeable) validateApproval(operator) {
super.setApprovalForAll(operator, approved);
}
}
Here is a simple collection operator allowlist checklist you should follow to ensure your game has no delays at launch:
- Have you imported
OperatorAllowlistEnforced.sol? - Have you implemented the allowlist check on transfers?
- Have you implemented the allowlist check on approvals?
The use of the preset contracts accelerates integration with Immutable's ecosystem. If your studio has developed custom ERC721 or ERC1155 collections, ensure they adhere to their respective standards in addition to inheriting the OperatorAllowlistEnforced.sol contract, to safeguard compatibility with Immutable's ecosystem.